Low-temperature rolling technology is a rolling technology that reduces the reheating temperature of steel billets below the non-recrystallized austenite zone and below the conventional hot rolling temperature. Low-temperature rolling technology can reduce total production energy consumption, improve the mechanical properties of steel billets, simplify heat treatment processes, and have high economic benefits, production efficiency, and product competitiveness. However, there are still some challenges in low-temperature rolling technology, such as high rolling mill load, reduced product plasticity, and frequent roll failures. This article elaborates on the main characteristics of low-temperature rolling technology, analyzes the impact of low-temperature rolling technology on products from the perspectives of mechanical properties and surface quality, points out the current problems of high rolling mill load and roll material failure in low-temperature rolling technology, and proposes methods to optimize the rolling quantity of each pass, adjust the rolling rate and number of passes based on the performance characteristics of the rolled parts, and improve the thermal fatigue performance of the roll material to reduce the rolling mill load. The article also discusses the development direction of future low-temperature rolling technology in the performance of cemented carbide rollers and the microstructural changes during the low-temperature rolling process.

WC-TaC-Co cemented carbides with plate-like WC grains were fabricated by vacuum sintering. The effects of TaC content on the microstructures and mechanical properties of cemented carbides with plate-like WC grains were studied by differential scanning calorimetry (DSC), X-ray diffractometry (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectrometer (EDS). The results show that with the increase of TaC content, the average size of WC grains first decreases and then increases, and the average length-thickness ratio first slightly increases and then decreases. Moreover, as TaC content rises, transverse rupture strength (TRS) gradually decreases, while the hardness and fracture toughness (K_IC) initially increase and subsequently decrease. Cemented carbides with 0.5% TaC exhibit great mechanical properties with a hardness of 91.5 HRA, a TRS of 2 617 MPa, and a K_IC of 15.4 MPa·m^1/2, respectively.

Tungsten oxide is an important raw material for the industrial production of tungsten powder. In addition to conventional physical performance testing of powder, the current phase detection methods are usually the K-value method or external standard method, but they mainly distinguish from the chemical composition such as the apparent yellow, blue, and purple and oxygen index. There are still shortcomings in guiding the production process. This article attempts to use the Rietveld method to characterize the phase structure of industrial tungsten oxide and weaken the influence of difficulties in tungsten oxide phase analysis through structural model assumptions and fitting conditions. The results of a series of process experimental samples indicate that the premise assumption of the method is feasible and suitable for phase analysis of industrial tungsten oxide at different production stages. Under specific processes, during the transition from yellow tungsten to blue tungsten, the anorthic phase of WO₃ decreases rapidly, and the monoclinic phase decreases, but the speed is relatively slow, while the orthorhombic phase increases. During the transition from blue tungsten to purple tungsten, the monoclinic and anorthic phases of WO₃ first disappear, while the orthorhombic phase gradually decreases, forming WO_2.90 monoclinic phase, followed by WO_2.90 tetragonal phase, and further generating WO_2.72 monoclinic phase. When the mass fraction of measured phase is more than 5%, the relative standard deviation can be less than 5%.

The abnormal grain growth of cemented carbides is the root cause of brittle fractures. In this study, the same tungsten (W) powder was distributed into three groups for carbonization. The carbonization process was performed for 1 h at 1 750 ℃, 1.5 h at 1 650 ℃, and 2 h at 1 550 ℃, during which three kinds of fine WC powder were prepared. Then, the WC powder was prepared into WC-10% Co cemented carbides through the same process. The properties of WC powder and differences in the microstructure of cemented carbides were compared. The results show that the WC powder prepared by different carbonization processes and the prepared cemented carbides show different properties. To be specific, WC powder prepared at 1 550 ℃ for 2 h shows W₂C, and the maximum abnormal grain growth of cemented carbides is 21 μm. The cemented carbides of WC powder prepared at 1 650 ℃ for 1.5 h display a maximum abnormal grain growth of 18 μm, and those of WC powder prepared at 1 750 ℃ for 1 h present a maximum abnormal grain growth of 14 μm. Therefore, it can be concluded that high temperature and short duration of carbonization are conducive to obtaining WC powder with complete crystals and large sub-grain size, and the cemented carbides prepared are uniform in microstructure, which subdues the abnormal grain growth.

In the current situation, international crude oil prices are rising. The rapid recovery trend of oil drilling activity has put forward higher requirements for PDC drill bit, PDC composite disc, and cemented carbide used in oil and gas exploration. This article summarizes the current status of the oil and gas extraction industry as well as the competitive situation of PDC composite sheet, with a focus on introducing the basic structure and current status of the synthesis process and related technology development for PDC drill bits. Focused on the key technologies that need to be breakthrough, such as binder phase replacement technology, gradient PDC composite sheet technology and cobalt removal technology, the suggestions for the development of high-quality bonded or unbonded phase, multi-layer structure and green production are proposed.

In this paper, WC-6%Co-(0~1.0%)-VC ultrafine grained cemented carbide was prepared by sintering at 1 450 °C for 1 h using the powder metallurgy method. The effects of VC addition on the average grain size, particle size distribution, three-dimensional morphology, and mechanical properties of WC were studied. The results showed that with the increasing VC addition, the average grain size of WC decreased rapidly at first and then slowly, and the particle size distribution became narrower. The hardness of WC-6%Co-VC ultrafine grained cemented carbide increased rapidly first and then slowly, while the fracture toughness decreased rapidly first and then slowly, and the flexural strength increased first and then decreased sharply. With the addition of 0.25%VC, the WC morphology changed from a truncated triangular prism to a stepped triangular prism. With the increase in VC content, the number of steps on the WC (0001) crystal plane increased, and the increase in the number of steps would significantly reduce the fracture toughness and flexural strength of the alloy; WC-6%Co-0.25%VC cemented carbide had the best comprehensive properties, and its Vickers hardness, fracture toughness, and flexural strength were 18.82 GPa, 8.87 MPa·m^1/2, and 3 190 MPa.

In this paper, the effects of Cr₃C₂ addition amount on the particle size, morphology, and mechanical properties of ultrafine grained WC-6%Co-(0~1.0%)Cr₃C₂ cemented carbide were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and property detection. The results show that the average grain size of WC decreases rapidly at first and then slowly with the increase in the Cr₃C₂ addition amount. The addition of 0.25% Cr₃C₂ induces the anisotropic growth of WC grains, and the morphology of WC grains is a quasi-triangular prism. With the increase in the Cr₃C₂ addition amount, the morphology of WC grains becomes more regular and finally becomes a triangular prism. With the increase in the addition amount of Cr₃C₂, the hardness of ultrafine grained WC-6%Co-Cr₃C₂ cemented carbide first increases rapidly and then slowly, but the fracture toughness gradually decreases, and the bending strength first increases and then slowly decreases. When 0.6%Cr₃C₂ is added, the comprehensive performance of WC-6%Co cemented carbide is the best, and its Vickers hardness, bending strength, and fracture toughness are 18.42 GPa, 3 450 MPa, and 9.32 MPa·m^1/2, respectively.

The photovoltaic industry is a strategic emerging sector in China. Crystalline silicon solar cells are a highly prominent class of cells in the photovoltaic industry. Compared to high-carbon steel wire substrate, the use of high-strength and highly ductile tungsten wire substrate for diamond coating can better meet the demand for efficient and high-quality cutting of ultra-thin monocrystalline silicon, a key material for crystalline silicon solar cells. Improving strength and toughness is fundamental to increasing the qualified product rate of tungsten wire drawing, achieving high-quality drawing for ultra-fine tungsten wire, and improving the cutting efficiency of ultra-thin monocrystalline silicon. The main methods used to strengthen and toughen tungsten are thermomechanical pressure processing, alloying, grain size and grain morphology control. In this paper, the implementation plans and effects of various strengthening and toughening strategies for tungsten materials are reviewed to provide an effective reference for the R&D of the second generation of ultra-fine photovoltaic tungsten wires with high strength and toughness. The strategies mainly include thermo-mechanical pressure machining enhancement, solid solution strengthening, second phase strengthening, and fine crystal strengthening.

The lattice constants, elastic constants, electronic structure, and charge distribution of Ti(C_0.5N_0.5) doped with metal W atoms were calculated and analyzed by using the first-principles method of density functional theory (DET). The results show that W atoms can exist in (Ti_1-xW_x)(C_0.5N_0.5) stably, but the addition of W atoms decreases the stability of the (Ti_1-xW_x)(C_0.5N_0.5) system, enhances the bonding energy among atoms, and distorts the lattice as Ti atoms and W atom shave different diameters. With the increase in W content, lattice distortion and lattice constant imbalance will be aggravated. The results of elastic constant calculation show that the appropriate addition of W atoms can improve the deformation resistance and hardness of (Ti_1-xW_x)(C_0.5N_0.5) and reduce the brittleness of the crystal. When x(W) = 12%, the deformation resistance and hardness of (Ti_1-xW_x)(C_0.5N_0.5) are the best. The theoretical hardness HV is increased by 6%. The calculation results of the electronic structure show that the state density increases at the Fermi level after doping W atoms, and the conductivity of (Ti_1-xW_x)(C_0.5N_0.5) is enhanced, which is much higher than that of Ti(C_0.5N_0.5). The charge difference density diagram shows that W atoms doping and replacing Ti atoms will form a polar covalent bond with C atoms, which can improve the inherent mechanical properties of (Ti_1-xW_x)(C_0.5N_0.5).

Internal stress affects the microstructure and physical properties of coatings and is a key detection indicator in coating preparation. Among non-destructive testing methods, the application of the X-ray diffraction stress measurement method, such as sin2ψ method has been widely reported. However, the side-incline method mode is often used in CVD coatings with the α-Al₂O₃-TiCN system, and there is little discussion on other measurement mode. This article attempts to characterize the residual stress of CVD multilayer coatings based on cemented carbide by using the Rietveld with glancing method assisted by the side-incline method and explore the stress distribution of each coating phase in the direction of coating deposition within TiN-Al₂O₃-TiCN system. Experiments have shown that when TiN is not sandblasted, the skin surface have been subjected to compressive stress. After sandblasting, the compressive stress decreases monotonically from the skin surface to the substrate. However, when the sandblasting force is too high, the stress release causes a decrease in the stress value of the skin surface. Before and after sandblasting with Al₂O₃, there is a trend of changing from compressive stress to tensile stress. The stress variation trend of MT-TiCN is similar to that of Al₂O₃, but due to its relatively maximum depth from the surface and similar phase structure to TiN, the analysis results are easily affected by other factors, such as differences in diffraction intensity, uneven sample thickness, or coating thinning and stress release caused by excessive sandblasting force. The test results of a series of process test samples demonstrate that this method has high reliability.

This paper takes the patent data in the field of cemented carbide in China and abroad as the research object, constructs the three-dimensional factor system of patent technology, economy, and law that affect the patent value, uses the multiple linear regression model to explore the influencing factors of the patent value in the field of cemented carbide, and excavates the differences of the factors that affect the patent value in the field of cemented carbide in China and abroad. The number of countries and the number of claims have a significant positive effect on the patent value in the cemented carbide field, while the number of patent families has a significant negative effect on the patent value in the cemented carbide field, and the significance is not affected by the region of the patent application. The factors that have a significant positive effect on the patent value in the field of cemented carbide in the influence factor system of China are the number of countries, the number of pages of literature, the number of claims, the number of IPC categories, and the number of independent claims according to the degree of influence, and the factors that have a significant negative effect are the number of patent family, the number of cited patents, and the number of patent applications. The factors that have a significant positive effect on the patent value in the field of cemented carbide in the influence factor system of other countries are the number of patent applications, the number of countries, the number of cited patents, the number of claims according to the degree of influence, and the factor that has a significant negative effect is the number of the patent family. By comparing the empirical results of the factors affecting the patent value in the field of cemented carbide in China and abroad, it is found that the number of cited patents and the number of patent applications have a significant negative impact on the patent value in the field of cemented carbide in China but have a positive impact on the patent value in the field of cemented carbide in other countries. Suggestions to enhance the patent value in the field of cemented carbide are as follows. The first is to promote collaborative innovation among industry, university, and research and the flow of technical knowledge in the cemented carbide field. The second is to apply the strategic layout of overseas cemented carbide patents to enhance the competitiveness of patented products. The third is to strengthen the quality management of patent documents and improve the judicial protection level of intellectual property rights for cemented carbides.

The surface oxidation behavior and effect on alloy properties of Four commonly used high-performance ultra-fine cemented carbide rods were studied by heating them in air and low vacuum to 300~1 000 ℃ and holding them for different time. The results show that in an air atmosphere, there is no oxidation observed in ultra-fine alloys at temperatures below 400 ℃. However, at temperatures above 500 ℃, the alloy undergoes significant oxidation, with the surface becoming noticeably rough and ultimately completely oxidized. In a low vacuum atmosphere, when the temperature is 600 ℃ or above, the alloy undergoes oxidation, and the oxide layer is relatively thin. When the alloy is heated to 500 ℃ in the air, CoWO₄ and WO₃ phases appear. As the holding time increases from 30 minutes to 120 minutes, the thickness of the oxide layer increases, and the proportion of CoWO₄ and WO₃ gradually increases. When the alloy is heated to 800 ℃, the proportion of CoWO₄ and WO₃ tends to stabilize, and the alloy surface has completely oxidized. The oxidation resistance of ultra-fine cemented carbide increases with the cobalt mean free path, and a larger surface area of cobalt indicates that it is easier to be oxidized into CoWO₄. Due to the volume expansion and loose morphology of CoWO₄ and WO₃, oxygen infiltrates through the fluffy oxide layer, leading to intensified alloy oxidation. As oxidation progresses, there is no significant change in the coercive force, cobalt magnetism, and hardness of the alloy, and the transverse rupture strength of the alloy decreases. After removing the oxide layer, the transverse fracture strength of the alloy is equivalent to that without oxidation, indicating that the decrease in transverse fracture strength of the alloy after heating and oxidation is mainly caused by surface oxidation. After removing the oxide layer from the oxidized sample, the alloy is made into precision micro drills and milling cutters, with a service life comparable to that before oxidation.

Binderless WC cemented carbide (binderless tungsten carbide, BTC) has excellent wear resistance, corrosion resistance, polishing performance, and oxidation resistance, which are unparalleled compared with traditional cemented carbide. It has a good application prospect in erosion-resistant and high wear-resistant tools, fine tools, oil and shale gas exploitation, and other fields. One of the key problems in the preparation of ultrafine/nanocrystalline BTC is to control the growth of WC grains. In this paper, the related research results of ultrafine/nanocrystalline BTC were reviewed from the aspects of preparation technology of ultrafine/nanocrystalline WC powder, material composition design of BTC, and molding process and sintering technology. The key role of raw material WC particle size, addition of second phase compounds, and advanced molding process and sintering technology in the densification process of BTC was emphasized. The performance differences of ultrafine/nanocrystalline BTC materials under different composition systems and different sintering processes were compared. It was pointed out that the main problems in the preparation process of ultrafine /nanocrystalline BTC were densification and strengthening and toughening, which could be solved by various advanced sintering technologies and developed second phase strengthening and toughening technologies, but they have not yet achieved industrial application. Finally, it was clarified that the development trend of ultrafine/nanocrystalline BTC was to obtain finer dense sintered bodies at low temperatures and low pressures.

In metal cutting, cemented carbide tools will oxidize at high temperatures, and their hardness will decrease significantly, which seriously affects the service performance of the tools. In this paper, WC-Co-based cemented carbides were prepared by the traditional powder metallurgy process. The effects of cobalt content, WC grain size, and TaC/NbC/TiC additives on oxidation resistance and hardness of cemented carbides at high temperatures were studied. The results show that with the increase in cobalt content, the oxidation resistance of cemented carbides at high temperatures increases slightly, and the hardness increases significantly. With the decrease in WC grain size, the oxidation resistance of cemented carbides at high temperatures increases slightly, but the hardness decreases significantly. Compared with WC-Co-based cemented carbides, the addition of TaC has no significant effect on the oxidation resistance of cemented carbides at high temperatures. The addition of NbC reduces the oxidation resistance of cemented carbides at high temperatures, but that of TiC can significantly improve the oxidation resistance of cemented carbides at high temperatures. Moreover, the addition of TaC, NbC, and TiC can significantly improve the hardness of cemented carbides at high temperatures.

Three batches of WC-6% Co coarse grained cemented carbides with the same carbon content and similar average WC grain size were prepared by ball milling of a single WC powder and ball milling of two WC powders with different particle sizes. By analyzing the particle size distribution of WC grains, as well as the coercive force (H_C) and Fracture toughness (K_IC) of the alloy, the effects of different preparation processes on the particle size distribution, coercive force and Fracture toughness of WC grains were studied. The results show that different preparation processes have obvious effects on the particle size distribution of WC grains, cobalt phase dispersion uniformity and Fracture toughness of the alloy. When the average grain size of WC is similar, compared with the alloy produced by using one WC powder ball milling process, the particle size dispersion coefficient of WC grains is reduced by 8.9% and 15.6%, respectively. The distribution of WC grains is more uniform, and the coercive force of the alloy is increased by 0.2 kA/m and 0.4 kA/m, while the toughness of the alloy is increased by 2.5% and 10.8%.

WC-Co cemented carbide is widely used in the manufacturing industry, but how to select and design high-performance and low-cost binders is the current difficulty and hotspot in the field of replacing binders with cemented carbides. High entropy alloys (HEA) as binders can refine WC grains and improve the hardness, fracture toughness, corrosion resistance, and oxidation resistance of cemented carbide. This paper outlines the research progress of WC-HEA cemented carbide in terms of HEA binder composition design, WC-HEA preparation technology, microstructure, and comprehensive performance and describes the problems faced in this field such as poor sintering characteristics and susceptibility to phase transformation. It is intended to provide a reference for the exploration of the toughening mechanism of HEA as a binder phase and revealing the constitutive relationship between microstructure and mechanical properties of WC-HEA composites in subsequent research.

316L has excellent corrosion resistance and is currently the most widely used austenitic stainless steel. In this paper, 316L stainless steel was taken as the research object, and four cemented carbide inserts of EM (large rake angle), SM3(small chip angle), MM (small rake angle, and SF (large chip angle) with different groove structures were selected to be processed under the parameters of semi-finishing machining. The influence of different groove structures of stainless steel turning inserts on cutting performance was studied. The results show that the EM and MM inserts have the lowest cutting force. A smaller chip angle of the insert groove indicates a lower cutting force. Combined with the characteristics of the groove, it shows that the reasonable double rake angle design is conducive to reducing the cutting force, and the chip breaking ability of the inserts is mainly related to the size of the chip angle and the feed. In addition, when the chip angle is designed at 20°, good chip breaking performance can be obtained without causing a significant increase in the cutting force.

Titanium dioxide (TiO₂) has been widely studied in the field of photocatalysis due to its excellent photocatalytic activity. However, the high recombination rate of photogenerated carriers and wide bandgap of TiO₂ limit its application. In this work, TiO₂/WO₃ heterostructured nanocomposite photocatalysts with oxygen vacancy defects were synthesized by introducing tungsten (W) into TiO₂. The introduction of oxygen vacancies reduced the band gap and broadened the light absorption range, while the heterojunction increased the photogenerated carriers and facilitated their separation. The experiment shows that TiO₂/WO₃ nanocomposite photocatalysts have enhanced photocatalytic activity, with up to 63.7 μmol of hydrogen produced from 100 mg of sample in 2 h. In addition, the TiO₂/WO₃ nanocomposite material shows excellent stability under simulated sunlight. This exploration provides new ideas for the design and preparation of TiO₂-based composite photocatalysts.

In view of the easy denitrification of the sintered body and the decomposition of N during the preparation of ultrafine-grained Ti(C,N)-based cermets by vacuum sintering, ultrafine-grained Ti(C,N)-based cermets are prepared by partial-pressure sintering with 130 Pa of nitrogen at 1 450 °C during the holding stage of the liquid phase, and the influence of the time of partial-pressure sintering under nitrogen on the microstructures and mechanical properties of cermets is investigated. The experimental results show that partial-pressure sintering under nitrogen can improve the uniformity of the internal structure of the sample. Under the influence of nitrogen, a Ni-rich layer will be formed in the outermost layer of the sample, and a TiN layer will be formed in the near-surface layer of the material. At the beginning of the partial pressure, the outermost layer of the sample is only the Ni-rich layer. With the increase in the partial pressure time, the black core phase in the near-surface layer of the organization dissolves under the influence of nitrogen, and the size of the black core phase decreases. The size of the annular phase increases until the black core phase gradually disappears, forming a Ti-rich (Ti,W)(C,N) solid solution, which is formed into the solid solution layer by merging the grown solid solution, As the partial pressure time increases, the titanium-rich solid solution reacts with N to form a TiN layer in the near-surface layer of the sample. The comprehensive mechanical properties of the sample are the best when the partial-pressure sintering time reaches 40 min, and its bending strength increases by 20% to 2 350 MPa. The Vickers hardness increases by 13.9% to 1 635 HV30, and the fracture toughness is not significantly improved.

A co-melting system of pure iron flux and tungsten-tin flux with cobalt-chromium-tungsten alloy powder sample was established, and the carbon content in cobalt-chromium-tungsten alloy powder was determined by high-frequency induction combustion infrared absorption carbon and sulfur detector. The experimental results show that the carbon content in cobalt-chromium-tungsten alloy powder with three different gradients can be accurately measured by mixing 0.30 g pure iron and 1.20 g tungsten-tin granules. In the process of melting, there is no spatter of the sample and the melt block spreading, and the peak-and-peak release curve is smooth and does not drag. The limit of carbon detection (3 s) is 0.000 34%, and the limit of carbon detection (10 s) is 0.0011%. The RSD (n=11) of the proposed method for the determination of the carbon to be measured ranges from 0.33% to 1.98%, and the recovery rate of the added standard ranges from 97.37% to 103.52%, indicating that the method has the characteristics of good accuracy and high precision for the determination of carbon content in cobalt-chromium-tungsten alloy powder and can meet the quality control analysis requirements of enterprises in the industrial production process. It can be applied to the daily analysis and testing work of third-party laboratories.

For the problem of cobalt pool in the production process of ultracoarse-grained cemented carbide, WC-8%Co ultracoarse-grained cemented carbide was prepared by spray drying granulation process, and the effects of the ball milling time and slurry-liquid ratio on cobalt pool and properties of the alloy were analyzed. The results show that the cobalt pool of ultracoarse cemented carbide can be eliminated by prolonging the ball milling time and increasing the slurry-liquid ratio. Under the conditions of a ball milling time of 12 h and a slurry-liquid ratio of 8.95 kg/L, ultracoarse cemented carbide with an average grain size of 7.36 μm is prepared, and the cobalt pool is not observed. The magnetic force of the alloy is 3.8 kA/m, and the transverse fracture strength reaches 1 820 N/mm². Under the condition of a ball milling time of 16 h and a slurry-liquid ratio of 5.20 kg/L, ultracoarse cemented carbide with an average grain size of 5.37 μm is prepared, and the cobalt pool is not observed. The cobalt phase is more evenly dispersed, and the alloy has a magnetic force of 4.2 kA/m and a transverse fracture strength of 2 230 N/mm².

FeNi alloy is widely used in oil exploration, aerospace, chemical industry, electronics, and other industries due to its excellent properties. The service environment of FeNi alloy is becoming more and more complex, and the current research on FeNi alloy mainly focuses on the impact of a single factor on its properties. Therefore, this paper studies the impact of temperature and humidity composite environments on its properties. The storage test of temperature and humidity composite environment for 10, 15, and 25 d is carried out with alternating humidity and heat box. The magnetic direct current (DC) test system and electrochemical system are used to test the sample and study the evolution law of its properties. The results show that with the extension of time, the magnetic property and corrosion resistance of FeNi alloy decrease. When the FeNi alloy is stored for 25 d under the cyclic temperature and humidity composite environmental test conditions, the maximum permeability μ_m, saturation magnetic induction B_s, and coercivity H_c retention rates are 98.06%, 98.98%, and 97.63%, respectively, The electrochemical polarization curve shows that the corrosion resistance of FeNi alloy will also weaken with the increase in test time. When stored for 25 d in a temperature and humidity composite environment, the corrosion current density of FeNi alloy material is 2.594 × 10⁻⁶ A·cm⁻², and the corrosion potential is −0.324 V.

Mo₂FeB₂-based cermets, synthesized from Mo, Fe, Cr, Ni, FeB, and C via a reaction boronizing sintering technique, are characterized by their exceptional hardness, strength, and toughness, coupled with comparatively economical production costs. This study delved into the fabrication of Fe-44.4%Mo-4.9%B-2.5%Cr-2.9%Ni-based cermets utilizing avacuum liquid phase sintering method and meticulously examined the morphological evolution, growth processes, and underlying mechanisms of the cermet’s hard phase at both solid and liquid phase sintering stages. The results reveal that below 600 °C, Fe amalgamates with lamellar FeB, initiating the formation of the Fe₂B phase and marking the onset of solid-phase sintering. As the temperature ascends to 900 °C, Mo commences nucleation at the Fe₂B interface, leading to the formation of Mo₂FeB₂ characterized by spiral growth patterns and the emergence of growth steps. Further temperature elevation to 1 000 °C propels the enlargement of Mo₂FeB₂ grains, surpassing critical radii and instigates the precipitation of diminutive Mo₂FeB₂ grains. At 1 050 °C, ongoing dissolution and precipitation processes result in the development of Mo₂FeB₂ grains with hexagonal cross-sections. Throughout this thermal trajectory, Mo₂FeB₂ grain growth traverses through four stages: nucleation, spiral growth, dissolution-precipitation, and the eventual establishment of hexagonal cross-sectional grains, culminating in the formation of hexagonal Mo₂FeB₂ grains derived from Mo, FeB, and Fe₂B phases. Beyond 1 050 °C, the cermets transition into the liquid phase sintering stage, characterized by columnar growth of the Mo₂FeB₂ hard phase. The growth activation energies determined for the long and short axes of the grains are 317 kJ/mol and 402 kJ/mol, respectively, suggesting a pronounced propensity for Mo₂FeB₂ grains to elongate along their long axis, ultimately yielding elongated grain structures.

The surface of 30CrMnSiA was coated with WC-10%Co4%Cr coating by high velocity oxygen fuel (HVOF) spraying technology. Based on the methods of orthogonal experimental design, three factors and three levels of orthogonal experiments were carried out to systematically study the effects of three main process parameters, namely kerosene flow rate, oxygen flow rate, and spraying distance, on the porosity, microhardness, bonding strength, powder rate, and residue stress of WC-10%Co4%Cr coating by HVOF spraying. The R value analysis results of the orthogonal test show that the kerosene flow rate is the main factor affecting the coating porosity, and the coating porosity is negatively correlated with the kerosene flow rate. The kerosene flow rate is also the main factor affecting the microhardness of the coating, and the coating microhardness is positively correlated with the kerosene flow rate. The spraying distance is the main factor affecting the bonding strength of the coating, and the bonding strength is negatively correlated with the spraying distance. The main factor affecting the powder rate is the kerosene flow rate, and the powder rate is negatively correlated with the kerosene flow rate. The main factor affecting the residual stress of the coating is the spraying distance, and the residue stress is negatively correlated with the spraying distance. The research on the influence of spraying parameters on coating properties is conducive to obtaining the coating with desired properties in the future.

This article discussed the production of cobalt powder through the hydrogen reduction process using two different forms of cobalt carbonate as raw materials. The powder characteristics were analyzed using scanning electron microscopy, laser particle size analyzer, Fischer particle size analyzer, and apparent density tester. The influence of the cobalt powder production process on the apparent density of powder was studied. The results show that the reduction temperature during the cobalt powder production process, the particle size and morphology of cobalt carbonate, and the particle size distribution of cobalt powder are direct influencing factors. Higher reduction temperature leads to a higher apparent density of produced cobalt powder. Larger particle size and more spherical morphology of cobalt carbonate result in higher apparent density of produced cobalt powder. The apparent densities of cobalt powder reduced at 620 °C from cobalt carbonate with particle sizes of 1.03 μm and 5.28 μm are 2.40 g/cm³ and 2.71 g/cm³, respectively, both higher than the cobalt powder reduced at 400 °C. Mixing cobalt powders of different sizes uniformly can improve the apparent density of the powder. When 20% of fine particles with a Fisher size of 1.50 μm and apparent density of 1.45 g/cm³ are thoroughly mixed with 80% of coarse particles with a Fisher size of 5.40 μm and apparent density of 2.71 g/cm³, the resulting apparent density is 2.93 g/cm³.

Ti(C_0.5,N_0.5) - 20%WC-8%TaC-5%Mo₂C-22%FeCoCrNi (A) and Ti(C_0.5,N_0.5)-20%WC-8%TaC-5%Mo₂C-22%CoCrNi (B) cermets were prepared by using (Fe)CoCrNi high and medium entropy alloy atomized powders, respectively. Ti(C_0.5,N_0.5)-20%WC-8%TaC-5%Mo₂C-12%Co-12%Ni (C) with the same binder metal volume ratio was used as the reference alloy. The electrochemical experiment results show that despite the presence of decarburization phase (η phase) and poor microstructure homogeneity, compared with the cermet C without microstructure defects, in H₂SO₄ (pH=1), Na₂SO₄ (pH=7), and NaOH (pH=13) solutions, the values of average self-corrosion current density (J_corr) for cermets A and B are decreased by 33% and 88%, and the values of average charge transfer resistance (R_ct) are increased by 97% and 219%, respectively. The defects of microstructures do not affect the improvement of corrosion resistance. In the H₂SO₄ solution, J_corr for cermet B is decreased by 89%, and R_ct is increased by 750%. The corrosion resistance of cermets in extremely corrosive media can be significantly improved by using CoCrNi medium entropy alloy as the binder metal. The formation mechanism of heterogeneous structure accompanied by the formation of η phase in cermets A and B is discussed from the perspective of intrinsic properties of high and medium entropy alloys and the wettability of the alloy system.

Ti(C,N) solid solutions with different carbon and nitrogen (C/N) ratios and Ti(C,N)-based ceramics with NbC, TaC, VC, and Cr₃C₂ added separately were prepared. The effects of different compositions on the thermal shock resistance of Ti(C,N)-based ceramics were studied by means of water quenching. The results show that the ceramic phase cracks are observed under the action of thermal stress during the thermal shock process of the ceramics, and the microcracks in the crack propagation path can promote crack propagation. Among Ti(C_x,N_y) solid solution ceramics with different C/N ratios, Ti(C_0.7,N_0.3) ceramic with a C/N ratio of 7/3 has the best thermal shock resistance, and the critical thermal shock temperature is 240 °C. Among the four added carbides (NbC, TaC, VC, and Cr₃C₂), the thermal shock resistance of the ceramics is significantly improved by NbC and TaC, and TaC is better than NbC, while the addition of VC and Cr₃C₂ is not conducive to the thermal shock resistance of the ceramics.

As a raw material for the production of cemented carbide, the quality control of tungsten carbide (WC) powder is extremely important. Currently, there are many testing indicators for quality monitoring, but it has been found during the production process that although the results of the indicators are similar, the quality of the powder still varies. It can be seen that the existing indicators are not comprehensive, and it is necessary to conduct a more accurate characterization of WC powder. This paper attempts to use multiple crystallinity sub-indexes to characterize the phase structure differences of WC powder and proposes the concept of crystallization index for quantifying the results of multiple indicators. Experiments have shown that the new indicator can effectively characterize ultrafine-to-ultracoarse grade WC powder, which is an effective supplement to existing indicators and has high method reliability. The quantitative results can be consistent with the trend of changes in process parameters such as carbonization temperature, amount of grain inhibitor added, and crushing method. Except for the index with a value approaching zero, ultrafine and fine grade WC powder has RSD<3% for each sub-index; Medium-to-coarse grade WC powder has RSD<5% for each sub-index; ultracoarse grade WC powder has significant fluctuations in D2 indicators, with RSD<10% and RSD<5% for other indicators.

The method for the determination of impurity elements including arsenic, cadmium, lead, zinc, antimony, bismuth, tin, cobalt, copper, manganese, magnesium, aluminum, iron, calcium, molybdenum, and silicon in carbonyl nickel powder by inductively coupled plasma atomic emission spectrometry was established. Nitric acid (3+2) was used to dissolve the sample, and the effect of acidity on the determination was investigated. The optimal analytical spectral lines for each element were determined. At the range of 0, 0.025, 0.1, 0.5, and 1.0 μg/mL, the intensity and concentration of 16 elements showed a good linear relationship, and the corresponding correlation coefficients were all more than 0.999. The final recoveries were 94.0%~104.0%, and the relative standard deviation RSD was less than 6.53% (n=7). The method can effectively improve the efficiency of multi-element analysis in carbonyl nickel powder and meet the requirements of the cemented carbide production process.

Polycrystalline diamond compact (PDC) is a kind of super hard composite material for oil and gas drilling and mineral mining. It needs to remove cobalt in the diamond layer to improve wear resistance and impact resistance. In this paper, hydrochloric acid, sulfuric acid, and Lewis acid (FeCl₃) were used as cobalt removal reagents, and the pressurized chemical precipitation method was used to remove cobalt in the PDC. The effects of raw material ratio, reaction pressure, and reaction time of cobalt removal reagents on the cobalt removal efficiency and properties of the PDC were studied. The results show that the cobalt in the PDC can be efficiently removed by the pressure chemical precipitation method. The PDC reacted with the cobalt removal reagent of 60 mL. The HCl concentration in the cobalt removal reagent was 6 mol/L; sulfuric acid dosage was 60 ml/L; Lewis acid dosage was 50 g/L; the reaction temperature was 160 ℃, and the reaction pressure was controlled at 0.8 MPa, which were the optimal cobalt removal conditions. Under these conditions, the cobalt removal depth reached 580 μm after 72 h, which met the 1.2 mm cobalt removal requirement of the PDC (cobalt removal depth > 0.5 mm). The cobalt removal efficiency of the pressurized chemical precipitation method was higher than that of the conventional acid leaching method. After cobalt removal, the wear resistance of the PDC was higher, and the impact toughness was better.

WC-9%Ni (mass fraction) cemented carbide was prepared by powder metallurgy process using Ni as binder phase. The effects of WC particle size and carbon content on the microstructure and properties of WC-9%Ni cemented carbide were studied by means of the optical microscope, hardness tester, and X-ray diffraction analyzer. The experimental results show that the grain size of the alloy is less affected by the carbon content and increases with the increase in WC particle size. The hardness of the alloy decreases with the increase in carbon content and the increase in WC particle size. The highest Rockwell hardness of the alloy prepared by WC of 1.78 μm and 2.4 μm is 88.6 HRA and 87.5 HRA, respectively, and the highest Vickers hardness HV30 is 11.9 GPa and 11.0 GPa, respectively. The coercive force and specific saturation magnetization of the alloy are extremely low. The fracture toughness of the alloy decreases with the increase in carbon content and increases with the increase in WC particle size. The flexural strength is less affected by the carbon content and decreases with the increase in WC particle size.

In this paper, polyethylene glycol, stearic acid, alcohol-soluble polyurethane resin, dibutyl ester, and polyoxyethylene stearates were used as raw materials. A new pressing binder composed of stearic acid and alcohol-soluble polyurethane resin with a mass ratio of 1:1 was developed based on the results from the ethanol dissolution test, sieving test, and drum test, which could well satisfy the requirements of the modern spray drying process. The cemented carbide mixtures doped with new pressing binder show better fluidity (33 s/25 cm³) and apparent density (3.27 g/cm³) compared with polyethylene glycol, paraffin wax, and butadiene rubber, and a lower pressing pressure (15.5 kN) is required during pressing. The sintered samples exhibit a more uniform microstructure and lower carbon residual (0.024%), showing that the prepared pressing binder is ideal for cemented carbide.

The comprehensive performance of cemented carbide can be improved by using a multi-component alloy instead of Co as the binder phase. In this paper, the research progress of WC-based cemented carbide prepared by using multicomponent alloy as a binder phase in recent years was systematically reviewed from the aspects of binder phase composition, alloy structure, and properties. The phase transformation behavior of the binder phase after multi-component alloy substitution and the influence of WC/multi-component alloy interface on the mechanical properties of cemented carbide were analyzed. It was proposed that the influence mechanism was the change of dislocation slip condition.

Single crystal and polycrystalline APT were selected as raw materials, and the particle size composition was screened and controlled. By comparing the morphology and particle size of WC powder prepared from APT with different crystal forms and particle size compositions as the initial raw material, as well as the number of coarse grains in the cemented carbide, the effect of APT crystal form and particle size on the physical properties and microstructure of WC powder and cemented carbides was studied. The results show that compared with polycrystalline APT, the WC powder prepared by single crystal APT with similar average particle size has a relatively smaller average particle size and more concentrated particle size distribution. At the same time, at different carbon contents and sintering temperatures, the cemented carbide prepared from WC produced with single crystal APT as the initial raw material has significantly fewer abnormally grown grains, and with the increase in sintering temperature and carbon content, the number of abnormally grown WC grains is significantly lower than the cemented carbide prepared from WC produced with polycrystalline APT. In addition, controlling the presence of coarse particles above 200 meshes in both single crystal and polycrystalline APT powders can significantly reduce the average particle size and dispersion of WC powder and obtain cemented carbides with fewer abnormally grown grains.

WC-4%Co-0.4%Cr₃C₂ alloy was prepared by ball milling at different time and sintering at different temperatures using three kinds of WC raw materials with different particle size distribution characteristics. The changes in microstructure and properties of the alloy were studied. The results show that it is easier to obtain the ultra-fine cemented carbide with uniform WC distribution and grain size when WC powder with concentrated particle size is used. After 50 h of ball milling and sintering of WC raw material with wide particle size distribution and more coarse bridge particles, the alloy with uniform microstructure can be obtained. At the same ball milling time, the microstructure of the alloys prepared with three different initial WC tends to be more uniform with the increase in sintering temperature; the WC grain growth in the alloy is more complete, and the Co phase distribution is more uniform. Although there are differences in powder morphology and particle size distribution of the three kinds of WC raw material, the microstructure and mechanical properties of cemented carbide obtained under the same sintering temperature and ball milling for 50 h tend to be consistent, and long-term ball milling can weaken the influence of initial WC agglomeration on the structure and properties of alloys.

Based on the forming principle of the involute, a mathematical model for solving the radius of the involute base circle of the indexable gear hob was proposed so that in some cases where the parameters such as the gear modulus and the radius of the pitch circle cannot be known, the radius of the involute base circle can be determined only according to the CAD model of the involute on the tool. The grinding mechanism of the peripheral edge grinder of the indexable tool was analyzed, and the mathematical model of indexable gear hob grinding was established. Therefore, the linkage point of the X-axis and the B-axis of the peripheral edge grinder of the indexable tool was obtained, and then the involute surface grinding test was carried out with a parallel diamond grinding wheel on the peripheral edge grinder. Ultra-depth-of-field microscope and image size measuring instrument were used to analyze the surface topography and dimensional error of the tool. The test results verify the accuracy of the mathematical model of the indexable gear hob grinding and provide a theoretical reference for the establishment of other gear hob mathematical models.

Vermicular graphite cast iron has unique physical characteristics, such as high cutting force, high cutting temperature, and poor cutting performance during the cutting process. The material characteristics of the insert have an extremely important impact on the cutting process of vermicular graphite cast iron. This article conducted a series of milling tests on vermicular graphite cast iron, compared the tool life of different insert materials when cutting vermicular graphite cast iron, analyzed the differences in wear morphology and causes of insert failure caused by matrix hardness, and studied the impact characteristics of insert wear status on subsequent processing during the initial cutting stage. The results show that the tool life of CVD-coated inserts is longer than that of PVD-coated inserts. The hardness of CVD-coated inserts that are made of WC-5.5%Co fine-grained alloy matrix with MT-TICN/Al₂O₃ coating with a matrix hardness of 15.97 GPa is moderate; the wear resistance of the coating is good, and the tool life of the insert is the highest. It is more suitable for milling vermicular graphite cast iron. By comparing the failure patterns of three kinds of inserts made of different materials, it is found that PVD-coated inserts that are made of WC-5.43%Co ultrafine-grained alloy matrix with TiAlN coating are more susceptible to breakage, and the CVD-coated inserts that are made of WC-6%Co fine-grained alloy matrix with MTTiCN/Al₂O₃ coating wear too fast, resulting in micro-breakage at the cutting edge. In addition, the CVD-coated inserts that are made of WC-5.5%Co fine-grained alloy matrix with MT-TiCN/Al₂O₃ coating have uniform wear in the flank. Through the analysis of the wear mechanism, it can be seen that the inserts made of three kinds of milling materials mainly have abrasive wear and adhesive wear. The PVD-coated inserts that are made of WC-5.43%Co ultrafine-grained with TiAlN coating have the coating exfoliation and micro-breakage at the cutting edge at the beginning of the cutting process. Without coating protection, the bare matrix is more prone to abrasive wear and adhesive wear. There are thermal cracks in the two kinds of CVD coatings at the initial stage of cutting, but no coating exfoliation occurs, especially for the CVD-coated inserts that are made of WC-5.5%Co fine-grained alloy matrix with MT-TiCN/Al₂O₃ coating with relatively higher matrix hardness. Since the support effect of the substrate to the coating is stronger, the cutting performance is better.

Ni-bonded cemented carbides are widely used in industry due to their corrosion resistance and low price. However, the relationship between the corrosion resistance and the alloy phase structure, especially the carbon precipitation state, has not been systematically studied. In this paper, samples with different carbon balance states were obtained by different sintering processes, and the microstructure and corrosion resistance of the cemented carbides were systematically characterized by metallography, X-ray diffraction (XRD), etc. The results show that there is free carbon in the Ni-bonded cemented carbides, but when in the decarburization or carbon balance state, the size of free carbon particles is smaller and dispersed; when in the carburized state, larger free carbon accumulates. The carbon content and sintering temperature both affect the carbon precipitation state of the cemented carbides. For nickel-bonded cemented carbides with different carbon balance states, the minimum corrosion current density is 3.14 × 10⁻⁷ A/cm², and the maximum corrosion current density is 1.04 × 10⁻⁶ A/cm². The maximum corrosion potential is −0.114 V, and the minimum corrosion potential is −0.199 V. Higher carbon content indicates a better corrosion resistance of Ni-bonded cemented carbides. Decarbonized phase reduces the corrosion resistance of Ni-bonded cemented carbides, and the free carbon phase enhances the corrosion resistance of Ni-bonded cemented carbides. The large number and dense distribution of decarburized phases also reduce the corrosion resistance of Ni-bonded cemented carbides.

The influence of different kinds of coated micro-drills on the processing performance and efficiency of IC packaging substrates was studied. The difficulties in mechanical drilling processing of IC packaging substrates, failure mechanisms of tools, and the characteristics of different high-performance coated micro-drills were analyzed. High-performance coated micro-drills were designed in view of several typical difficult-to-drill IC packaging substrates. Effective solutions for drilling quality assurance, efficiency improvement, and tool life improvement in drilling IC packaging substrates, especially difficult-to-package substrates, were obtained. The results showed that the wear resistance of the micro-drills could be significantly improved by diamond coating, especially packaging substrates with a high content of fillers that had a great impact on tool wear. Compared with uncoated micro-drills or other coated micro-drills, the tool life was significantly improved by diamond coating. Diamond-like carbon coating, with a low friction coefficient, was conducive to the rapid ejection of chips and the reduction of processing temperature and cutting force. The hole-wall roughness, hole position accuracy, and tool breakage rate were improved apparently when micro-holes of packaging substrates (such as FCBGA thick-core substrates) with large thickness-to-diameter ratios and difficult dust discharge were drilled. For micro-hole processing of thinner packaging substrates such as CSP, the tool breakage rate was reduced, and both the number of stacked substrates and drilling efficiency were increased by the diamond-like carbon coating.

Taking the treatment of ammonia waste gas in the acid extraction process of tungsten hydrometallurgy as an example, this thesis describes the sources and characteristics of ammonia waste gas and studies the basic mechanism of ammonia recovery. On this basis, according to the classified disposal during actual production, technologies such as (distillation and concentration + pressurized low-temperature water absorption) for ammonia waste gas from evaporative crystallization and (dust removal + pressurized low-temperature water absorption) for ammonia waste gas from calcination are proposed, forming a new method of efficient closed-circuit recycling treatment of ammonia waste gas and water in the whole process of tungsten smelting. The implementation effect is also tracked. Through the implementation of the new treatment method, the consumption of liquid ammonia is lowered by 66.7%; the efficiency of ammonia recovery is increased from less than 50% to more than 98%, and the emission of gaseous ammonia-contaminated factor is reduced from the source, producing significant economic and environmental benefits and providing a reference for environmental protection and emission reduction of tungsten smelting.