Cemented carbide is a composite material widely used in fields including aerospace, metallurgy, and construction. In the past decades, many traditional processes such as powder metallurgy and casting have been proposed to manufacture cemented carbide parts. Among them, additive manufacturing (AM) technologies can easily realize the production of complex geometric parts, which is expected to reduce the costs in the production and application of cemented carbide. On the basis of the classification by AM, this paper summarized the working principles, process optimization, part performance, and limitations of AM technologies for cemented carbide, such as selective laser melting (SLM), selective laser sintering (SLS), laser engineered net shaping (LENS), binder injection, and 3D gel-printing (3DGP). Additionally, the existing problems of AM for cemented carbide in part performance were pointed out, and the future development direction in process control, post-processing optimization, mechanism research, and combination with traditional processes was also discussed.

As a super-hard material with good thermal conductivity, diamond is an ideal material for precision machining tools and is also expected to become the next-generation semiconductor material. Regardless of the application background, the durability of diamond materials is of great importance, which has led to the study of diamond damage. In this study, in-situ scanning electron microscopy (SEM) was used to investigate the oxidative damage of diamond and the thermal contact damage between diamond and ferrous metals. Dynamic observations demonstrate that the number of nanodiamonds decreases at 400 ℃ during the oxidation process, and the oxidation of nanodiamonds is manifested as internal collapse due to the coating of the outer graphite layer. The bulk diamond, however, starts to suffer from oxidative damage at 800 ℃. During the oxidation process, an intermediate phase in the form of sp³-hybridized amorphous carbon appears on the diamond surface, and the selective oxidation of crystal planes occurs at 1 200 ℃. During the thermal contact between diamond and iron, γ- Fe becomes the dominant phase at 1 000 ℃ and etches the diamond surface through its ability to dissolve carbon. This study reveals the microscopic mechanisms of two kinds of diamond damage, which plays an important guiding role in the inhibition of diamond damage.

Cermets have become indispensable in manufacturing industry due to their excellent hardness, corrosion resistance and high chemical stability. In this case the research status quo of the typical cermets is reviewed, involving cemented carbide, Ti(C,N) based cements and ternary boride based cermets. The microstructure of ceramic phases and binder phases, preparation, and the applications of computational simulation in cermets design are elucidated. Finally, the outlook on novel materials design, processing, and research methods for cermets is presented.

In this paper, metallography, scanning electron microscopy (SEM), and energy spectrum analysis were conducted to study the cubic phases of the WC-Co cemented carbides and the impurity phases of regenerated cemented carbides. Specifically, the paper identified and analyzed these phases and discussed the microstructures and action mechanisms of the cubic phases to provide data support for the production process control of the company. The results show that the additives TaC and NbC added into the cemented carbides form the cubic phases in the form of (Ta, Nb, W)C cubic crystal carbides, and the impurity elements in regenerated cemented carbides constitute the impurity phases in the form of oxides and chlorides containing the impurity elements. The cubic phases and impurity phases in cemented carbides can be identified and analyzed by SEM and energy dispersive X-ray spectroscopy (EDS).

The evolution of microstructure and properties of Ti(C,N)-5%TaC-50%Ni cermets (mass fraction the same below) and Ti(C,N)-10%TaC-50%Ni cermets with temperature was studied by thermogravimetry-differential scanning calorimetry-thermogravimetry-quadrupole mass spectrometry (DSC-TG-QMS), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The results show that the white rim and white core begin to form in solid-phase sintering, but their formation modes are different, and the white core and white rim are finally formed by dissolution-precipitation in the early stage of liquid-phase sintering. The gray rim tends to form on the white core and white rim and develop some rimless structures at the same time. The content of Ti in the gray rim is higher than that in the white rim, to which the rapid decrease in Ti(C,N) stability at high temperatures should be attributed. The hardness of cermets with 5%TaC rises rapidly to 7,115 MPa with the increase in sintering temperature before it diminishes slowly to 6,791 MPa.

Carbonized polymer dots (CPDs) have drawn a lot of attention in the past ten years because of their excellent selectivity and sensitivity. In this study, tungsten was doped into CPDs (W-CPDs) using a simple hydrothermal technique for the first time. With an excitation/emission maximum of 365/454 nm and excitation-independent emission, WCPDs exhibit blue fluorescence and have an average particle diameter of 2.34 nm. Because of the dynamic quenching between Fe³⁺ and W-CPDs, there is a good linear relationship between the Fe³⁺ concentration and the limit of detection (LOD) of 0.02 μM for W-CPD fluorescence intensity. This technique enables quick detection of Fe³⁺ in drinking water and is expected to lower the risk of Fe³⁺ ingestion by humans.

After analyzing the existing built-in damping tool holders for boring, this paper designs a simple damping tool holder with a built-in vibration absorber by optimizing the structure of the vibration absorber. Modal tests and internal hole cutting tests are conducted to experimentally investigate the relationship between the size of the cavity, in which the vibration absorber is installed, at the front end of the main body part of the tool holder and the anti-vibration performance of the damping tool holder. The test results show that compared with the ordinary tool holder, the proposed damping tool holder achieves the following improvements. When the inner diameter of the cavity is 24 mm and its hole depth is 86 mm, the decay time of excitation response is shortened to 1/4, the damping ratio is increased by nearly 10 times, and the limit depth of cut is increased to about 0.88 mm. As a result, the anti-vibration performance is greatly enhanced. When the cavity is further increased to 26 mm in inner diameter and 92 mm in hole depth, the damping ratio keeps increasing slightly. Nevertheless, modal stiffness decreases greatly, response decay time increases, and the limit depth of cut decreases to 0.75 mm. Consequently, the anti-vibration performance decreases instead. The cutting test results show that when the depth of cut is 1 mm, the ordinary tool holder no longer works. The surface machined by the tool holder with a large cavity 26 mm in inner diameter and 92 mm in hole depth has a roughness of 5.125 µm, with obvious chatter marks. In contrast, that machined by the tool holder with a cavity 24 mm in inner diameter and 86 mm in hole depth has a roughness of 2.792 µm, bright and free of chatter marks. The results are basically consistent with the conclusion of the theoretical analysis of the stability curves.

For the production of targets and high-precision integrated circuit conductors, high-purity tungsten(5N-6N) is required. A high-throughput technique was used to prepare high-purity ammonium paratungstate (APT) in this study. Specifically, APT raw materials were processed by thermal dissociation in a multi-temperature zone tube furnace and then dissolved in ammonia water. Then, the phase of thermally dissociated APT at different temperatures was analyzed by in-situ XRD and conventional XRD, and the optimal ammonia dissolution treatment conditions were obtained upon the optimization of test parameters by orthogonal design. After several cycles of dissolution-filtration-cleaning-precipitation for purification, APT was calcined and reduced to obtain high-purity tungsten powder. Before and after purification, glow discharge mass

spectrometry was employed to test the purity of the materials. The results indicate that APT can be completely reduced in a 5% (volume fractions) mixed atmosphere of hydrogen and nitrogen at 800 ℃ for 10 h after three cycles of ammonia dissolution and precipitation, and the tungsten power, with the purity of 5N and average grain size of 670 nm, can be obtained℃. This study provides a research approach as well as a reference for the preparation and process optimization of high-purity tungsten oxide and tungsten powder.

Two kinds of tungsten carbide (WC) raw material with a respective carbon content of 5.90% (unsaturated carbon, mass fraction, the same below) and 6.15% (saturated carbon) were used to manufacture the rubber binder mixture and paraffin binder mixture of WC-6%Ni cemented carbides separately, and they were pressed into green compacts. Then, the relative magnetic saturation of the cemented carbides was changed by the adjustment to the debonding and dewaxing conditions of the green compacts to ensure that the cemented carbides presented two-phase (WC + Ni) or three-phase (WC + Ni + η and WC + Ni + C) microstructure. Finally, a comparative analysis was performed on the differences in microstructure and properties of WC-6%Ni cemented carbides prepared by unsaturated carbon raw material and saturated carbon raw material in the state of equivalent relative magnetic saturation. The results reveal that the WC-Ni cemented carbide has low specific saturation magnetization, but similar to the WC-Co cemented carbide, it can be used as an indicator to measure the carbon content of cemented carbides, and its ultimate relative magnetic saturation is about 90%. Due to the existence of the W₂C phase in unsaturated carbon raw material, the microstructure of the prepared cemented carbide is sensitive to the carbon content, and abnormal coarse grains are prone to occur. The density, hardness, and bending strength of the cemented carbide prepared by unsaturated carbon raw material are slightly higher than those of the cemented carbide prepared by saturated carbon raw material when the cemented carbides are in the non-magnetic conditions with a two-phase microstructure. When the relative magnetic saturation is about 80%, and the microstructure is in a two-phase condition, the density and hardness of the cemented carbide prepared by unsaturated carbon raw material are slightly higher than those of the cemented carbide prepared by saturated carbon raw material. Nevertheless, the bending strength of the cemented carbide prepared by saturated carbon raw material is 19.4% higher than that of the cemented carbide prepared by unsaturated carbon raw material. In production practice, we should use saturated carbon WC raw material to manufacture WC-Ni cemented carbides to obtain uniform microstructure and improve its comprehensive performance.

CVD coating is a surface treatment technology widely used in cemented carbide indexable inserts. TiN/MTTi(C,N)/α-Al₂O₃/TiN is one of the mainstream CVD multifunctional composite coating. The addition of CO in CVD deposition gas is a simple industrial way to control the structure and properties of MT-Ti(C,N) coating. In this research, single-layer MTTi(C,N) and typical two-layer MT-Ti(C,N)/α-Al₂O₃ coatings were prepared by adding CO in CVD deposition gas, and the effect of CO addition on the microstructure, mechanical properties, adhesion and cutting performance of the coatings were investigated. The results show that the addition of CO do not change the crystal structure of Ti(C,N) but changes the grain orientation of Ti(C,N), while Ti(C,N) grains are gradually refined with the increasing of the CO amount. In addition, changes in the CO amount results in the changes of the α-Al₂O₃ orientation and coating adhesion. When the volume fraction of CO is 1% and 2.5%, the coating exhibits good room-temperature adhesion and long continuous cutting tool life.

TiN/MT-TiCN/Al₂O₃/ZrCN multilayer coatings were firstly deposited on WC-Co cemented carbide by chemical vapor deposition and micro-blasted. The microstructure and properties of the coating were characterized by X-ray diffraction, scanning electron microscope, micro-hardness tester, scratch tester and reciprocating friction and wear tester. The thermal stability of the coating was studied by comparing the microstructure and mechanical properties of un-annealed coating, annealed coatings at 900 ℃ and 1 000 ℃. The results show that vacuum annealing has no obvious effect on the phase of the TiN/MT-TiCN/Al₂O₃/ZrCN coating. After annealed at 900℃, the hardness and adhesion strength of the coating decreases by 9.4% and 46.7% in contrast to those of un-annealed coating, respectively. After annealing at 1000℃, the hardness and adhesion strength of the coating decreases more significantly, decreasing by 15.6% and 59.5%, respectively. The TiN/MT-TiCN/Al₂O₃/ZrCN coating exhibits good thermal stability at 900 ℃. The friction coefficient of annealed coating is slightly bigger than that of un-annealed coating due to the increased surface roughness. Compared with un-annealed coating, the adhesive wear, abrasive wear and fatigue wear of annealed coating are aggravated due to the decreased residual compressive stress, hardness and adhesion strength. The wear resistance of annealed coating decreases.

Ternary borides have been widely used due to high hardness, low density, high wear resistance and high corrosion resistance. However, the ternary borides based cermets have lower mechanical properties when compared with WC-Co cemented carbide. The effects of TiB₂ particle additions on microstructure and mechanical properties of MoCoB-Co cermets sintered at 1 300 ℃ were investigated. The in-situ MoCoB and TiB₂ are the double hard phases of MoCoB-Co cermet. The MoCoB grains, which exhibitboth equiaxed and rod morphologies, are obviously refined. The ratio of MoCoB/Co gradually increases with the increase of TiB₂ content, but the grain size of equiaxed MoCoB remains 1~2 μm. When the content of TiB₂ is 15%~20% (mass fraction, the same below), the rod MoCoB grows and the minor axis increases significantly. The hardness of the cermet is improved with TiB₂ addition. When the TiB₂ content is 15%, the hardness reaches HRA 88.9, which is about 6% higher than that without addition.

Shallow surface microcracks in metals can directly affect the performance and service life of metals, and nonlinear ultrasonic detection methods have shown excellent results for detecting shallow surface defects. This paper studies the nonlinear ultrasonic laws of crack detection and positioning for shallow surface defects in steel through finite element simulation. The paper also establishes a two-dimensional frequency-mixing surface wave detection model that includes surface cracks in finite element simulation software, namely COMSOL, studies the nonlinear effects of ultrasound waves and surface cracks in steel, summarizes the relationship between defect size and side frequency signal amplitude changes, and uses an opposite-side frequency-mixing excitation scheme based on time-frequency analysis to study crack positioning. The simulation results show that when there is a crack on the metal surface, the sum frequency and difference frequency signals will appear in the echo signal received by the detection point, and the strength of the side frequency signal increases with the increase in crack width, attenuates with the increase in detection distance, and shows a trend of first increasing and then decreasing with the increase in crack depth; the positioning of surface cracks is realized by time-frequency analysis. By using ultrasonic signals with excitation frequencies of 0.5 and 0.8 MHz and a fundamental frequency amplitude of 10⁻⁵ m, shallow surface cracks with a depth of 0.2~2 mm and a width of 5~30 μm can be detected, and the positioning accuracy reaches 88%. These results provide a reference for the nonlinear frequency-mixing ultrasonic detection and positioning of shallow surface microdefects in steel.

In this paper, the coarse-grained cemented carbide mixture with cobalt content of 3%, 8%, 18% and 26% were selected for ball-milling. When the milling time was 15 h, 16 h and 17 h, the mixture was taken out and made into four groups of cemented carbide samples with three batches in each group. The effects of milling time on the WC grain size distribution and WC adjacency of coarse-grained cemented carbide were studied. The results show that the WC grain size distribution curve of the same group of coarse-grained cemented carbides gradually deviates to the left with the increase of milling time, the right branch of the distribution curve becomes steeper, and the WC adjacency decreases first and then increases. In the same group of samples, the alloy with the slowest change of the percentage of right branch of WC grain size distribution curve has the smallest WC adjacency. The characteristics of WC grain size distribution in the alloy with low WC adjacency are explained by the densest filling theory.

WC-10%Co4%Cr coatings prepared by the high velocity oxygen fuel (HVOF) technology had high hardness and good wear resistance and were widely used in petrochemical, aerospace, and other fields as an important material surface protection method. Since there were many factors affecting the properties of HVOF WC-10%Co4%Cr coatings, this paper summarized the effects of spraying powder characteristics, process, pretreatments, and post-treatments on the properties of HVOF WC-10%Co4%Cr coatings, reviewed the main research status in recent years, and proposed future development measures such as developing safer and more environmentally friendly spraying powder with multi-peak structure, further optimization of the HVOF spraying process, and combining the HVOF technology with other coating heat treatments.

Industrial cluster is an effective way to promote the rapid development of an industry. China’s cemented carbide industry has formed several prototypes of industrial clusters. The author analyzes the characteristics of cemented carbide industrial clusters in Zhuzhou and compares cemented carbide industrial clusters both in China and abroad. In addition, it is pointed out that there are some problems in China’s cemented carbide industrial clusters, such as insufficient consensus on industrial development directions, imperfect intellectual property protection systems, and incomplete product structures and service levels. As a result, the paper puts forward suggestions for China’s cemented carbide industrial clusters, including constructing industrial clusters featuring aircraft carrier battle groups, improving intellectual property protection systems, strengthening the integration of industry, education, and research, and enhancing the guidance of governments and industry associations, so as to promote the high-quality development of China’s cemented carbide industrial clusters.

The purpose of the paper is to explore the risk control measures for shield construction of metro tunnel. Based on the research data of metro shield tunneling at home and abroad, the construction risk of metro shield tunnel is analyzed, so as to understand the basic principle of metro shield tunneling method comprehensively. The characteristics and process of metro shield tunneling construction technology are elaborated, while the risk analysis is carried out and risk evaluation model is established. In view of the common risks that may occur during the construction of Metro shield, the concrete analysis is made and reasonable risk control suggestions are given. The final conclusion is obtained: strict control of the influence of environmental factors and human factors on metro tunnel shield construction can effectively avoid risks and ensure the safety of metro tunnel shield construction.

According the principle of phased array ultrasonic testing, the phased array ultrasonic testing block of grooved and ribbed cemented carbide roller was designed. By using this testing block and the specific probe with the corresponding wedge, the phased array ultrasonic testing equipment was adjusted and the sensitivity was debugged. With the inner surface of the slotted and ribbed roller as the contact surface, phased array ultrasonic testing was conducted at the groove and rib position of the roll by using the debugged equipment. Through experiment verification, the internal defects at the groove and rib position of the roll can be detected by this phased array ultrasonic testing method through scanning in the range of 40°~70°. And the location of defects can be accurately determined with the error range of 0~2 mm, which can accurate guide formulating the grinding parameters of the cemented carbide roll.

To study the effect of carbon content on the properties of WC-Co-Ni-Fe-Cr carbide, the influence law of carbon content variety on the microstructure and properties of cemented carbide is investigated based on the research object of WC-9.5%(Co-Ni-Fe-Cr). The research results indicate that WC average grain size grows along with the increase of carbon content, nevertheless, the WC grain size is comparatively uniformity, and no abnormal coarse grain size emerges even when carburization occurs. The decarburization and carburization have extreme influences on TRS property, both can cause significant decline of cemented carbide’s TRS property, especially the decarburization has the worst influences. The content of Cr and W in binder phase decreases with the increasing of carbon content, the decreasing of carbon potential causes high solid solubility, which has the same influence law as the WC-Co cemented carbide.

The effect of Nb-addition on the structure, mechanical and thermal properties of TiAlN coating deposited on cemented carbide, low-alloy steel, polycrystalline Al₂O₃ and tungsten substrates is investigated using differential scanning calorimetry, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and nano-indentation. In order to optimize the propertiy of TiAlN coating, Ti_0.46Al_0.54N, Ti_0.40Al_0.53Nb_0.07N and Ti_0.34Al_0.52Nb_0.14N coatings deposited by cathodic arc evaporation behave metastable face-centered cubic structure, and hardness values of 30.1±0.4 GPa, 29.7±0.4 GPa and 29.6±0.7 GPa, respectively. Alloying with Nb into TiAlN coating increases the H³/E² ratio and toughness. The thermal stability of TiAlN coating is improved by retarding the spinodal decomposition and w-AlN precipitation. After 10 h oxidation at 900 ℃ , the oxide scales of Ti_0.40Al_0.53Nb_0.07N and Ti_0.34Al_0.52Nb_0.14N coatings are 0.91 and 0.67 μm, while the Ti_0.46Al_0.54N coating has been completely oxidized.

The micro bending deformation of ultra small micro drill with ultra high aspect ratio was analyzed. The influence of different rotation speeds on the swing distance of the micro drill when it was not drilled into the plate is calculated by software. Then, the stress of the micro drill after drilling into the PCB was simulated, and the deformation of the micro drill in the flute length area with or without constraints was calculated. The influence of different constraint positions and constraint modes on micro bending deformation in the flute length area of micro drill was studied. A new type of micro drill with ultra high aspect ratio and a new self-aligning structure was developed and applied to machining the high communicating speed printed circuit board with 8 mm in thickness. Through hole machining is carried out by using the method of opposite drilling at both sides, and the influence of the structure of the micro drill and coating on the hole offset is tested. The result showed that the swing distance of drill bit increased from 0.02 mm to 0.6 mm as the rotation speed increased from 150 kr/min to 245 kr/min before the micro drill drilling into the board. After drilling into the board, the constraint structure was designed in the flute length area, which can effectively reduce the micro bending deformation. By preparing the super lubricating coating, the problem of tool breaking of ultra high micro drill was solved, and the hole offset was reduced simultaneously. Compared with the conventional micro drill, the coated new type micro drill can reduce the hole offset from 56µm down to 35µm, meeting the demand.

As an ideal fixation material in modern orthopedics, titanium based alloys have strong biocompatibility and corrosion resistance. They have become one of the important materials to replace hard tissue in the orthopedic clinic. In this study, the progress of improving biological properties by phosphorus ion implantation on the surface of medical titanium based alloys was reviewed. Firstly, the modification methods of ion implantation on metal surfaces were discussed. Then, the relevant research results after phosphorus ion implantation on the surface of titanium based alloys were analyzed, involving the improvement of corrosion resistance, biocompatibility, oxidation resistance and surface hardness. Finally, we provided an outlook on the application of phosphorus ion implantation on the surface of titanium based alloys to improve biological properties in medicine. Scholars in related fields are expected to try experiments such as high-energy implantation and multi-element implantation, so as to promote the development of titanium based alloys in the medical field.

The competition pattern of cemented carbide industry in the world and China in recent three years was compared horizontally, and the main financial and operational indicators of the main cemented carbide enterprises were compared longitudinally before and after COVID-19 pandemic. Market analysis of main cemented carbide products was conducted. The operation situation of domestic cemented carbide enterprises was combed. And the overall environment of the industry was analyzed. It can be concluded that the Chinese cemented carbide industry is still at recovering stage after the Covid-19 pandemic hits. Furthermore, the rapid recovering rate indicates that the market is growing significantly. However, Chinese cemented carbide industry is still facing an industry pattern of "large quantity, small size and scattered distribution", with insufficient R&D investment and weak competitiveness of high-end products. Therefore, it is suggested that in the period of economic recovery, Chinese cemented carbide industry should seize the market opportunity, make good use of the policy window, accelerate domestic substitution and increase the market share of high-end products. It should increase R&D investment, improve product quality so as to form core competitiveness. The industry ecology of large leading enterprises plus small high concentration enterprises should be established to realize the benign development of the industry.

Mo₂FeB₂ based cermet is characterized by high hardness, excellent wear-resistance, corrosion resistance, high temperature resistance and thermal shock resistance. Moreover, its coefficient of thermal expansion is similar to most of steel and iron materials. Thus, it shows great development potentiality and broad application foreground in the field of tool and mould materials, high-performance bearing, coatings (claddings), etc. In this paper, the chemical composition, microstructure and properties of Mo₂FeB₂ based cermets are briefly introduced. In particular, the effects of boron, carbon, rare earth, transition metal elements, and additional strengthening phase and grain growth inhibitor on its phase composition, density, grain size, hardness, transverse rupture strength and fracture toughness and their action mechanism are emphatically expounded. And then the preparation technologies of Mo₂FeB₂ based cermets and their coatings and claddings are summarized. Finally, it is proposed that the future research should be focused on the effects of alloying elements on mechanical properties and growth behavior of Mo₂FeB₂ phase and their action mechanism, and the reclamation techniques of discarded Mo₂FeB₂ based cermets, etc.

Both NbC and TiN_x have rock salt structure (NaCl structure) and excellent mechanical properties, but they are difficult to sintering and have brittless. In this paper, by means of spark plasma sintering (SPS), the effects of NbC contents (0%~40%, mass fraction) and sintering temperatures (1 300~1 600 ℃) on the microstructure and properties of TiN_0.3-NbC composites are investigated. It is found that in the process of sintering, TiN_0.3 diffuses with NbC to form single-phase (Ti,Nb)(N,C)_x solid solution. The experimental results show that when the sintering temperature is 1 600 ℃, with the increase of NbC content, the hardness and toughness of TiN_0.3-NbC composite increase first and then decrease. When the NbC content is 30%, the hardness and toughness reach the maximum at the same time, which are 22.4 GPa and 7.39 MPa·m^1/2, respectively. In addition, with the increase of sintering temperature, the toughness of TiN_0.3-15%NbC composite at 1 600 ℃ reaches 7.68 MPa·m^1/2, while the hardness of TiN_0.3-15%NbC composite at 1 500 ℃ reaches the maximum of 22.39 GPa.

Ti(C,N)-based cermets with different Cr contents were prepared by vacuum sintering (vacuum degree is less than 3 Pa). The oxidation resistance of Ti(C,N)-based cermets at 900 ℃ was studied. The results show that Cr can greatly improve the high temperature oxidation resistance of Ti(C,N)- based cermets. The oxidation layer of Ti(C,N) based cermets with Cr addition is multilayer, the main components of oxide layer are NiCr₂O₄, NiWO₃, NiTiO₃, and the main component of the transition layer is TiO₂. Compared with the cermets without Cr element, adding Cr element can generate more TiO₂ and NiTiO₃ phases and new phases of NiCr₂O₄ and CrMoO₄. The Gibbs free energy calculation based on thermodynamic data shows that the stability of the oxide is different, and the order of reaction is also different. W element and Cr element are oxidized first, followed by Mo, Ti, Ni. The oxides will continue to react in a high temperature environment to form more complex compounds to form the components of the oxide layer. According to the mechanism analysis, the oxidation can be divided into three stages: oxygen erosion into the matrix, oxide layer formation and oxide layer peeling.

In order to establish the mobility database for the design and development of NiCrAlCoSi high entropy alloy (HEA) bond coat, two BCC Cr-x (x=Co,Si)/Cr diffusion couples were prepared. The concentration profiles were obtained by EPMA, and the diffusion behaviors at 1 423 K and 1 473 K were studied. The results show that the interdiffusion coefficient of BCC Cr-x (x=Co, Si) binary system increases with the increase of temperature and slightly increases with the increase of elemental mole fraction.

1J50 soft magnetic material is often used as precision components in aerospace field because of its good performance. However, at present, 1J50 magnetic element is facing more and more complex and extreme use environment, which puts forward more stringent requirements. In this paper, 1J50 soft magnetic material is tested in the accelerated high temperature environment in the laboratory. The high temperature test is carried out in the high temperature test chamber at 80 ℃, 120 ℃ and 180 ℃ to study its performance evolution law.The results show that with the extension of storage time, the magnetic properties of 1J50 materials will be affected to a certain extent. In addition, the magnetic properties of 1J50 materials under three storage conditions decline obviously when the storage time is 2~66 d, and then decline slowly. The research results of this paper have certain significance for studying the adaptability of 1J50 material in high temperature environment.

The quality of the micro-hole processing of the printed circuit board (PCB) directly determines the stability and reliability of the inner and outer circuit connections. The tool structure is one of the main factors affecting the quality of the micro-hole processing. In this paper, by changing the drill point angle, the primary face angle and the secondary face angle of the micro-drill, the influence of the tool structure of the carbide micro-drill on the chip morphology, the axial force of the drilling, the wear of the micro-drill and the processing quality of the micro-hole drilling of high-speed printed circuit boards and flexible double-sided copper clad laminates is studied. The results show that the chip morphology of the high-speed board and the flexible board are short bends and long spirals, respectively. When high-speed boards and flexible boards are processed, increasing the drill point angle appropriately can effectively reduce tool wear and hole wall roughness, and also improve hole position accuracy. Changing the primary face angle has a significant impact on tool wear and hole wall roughness. The tool wear amount of micro-drills with the primary face angle of 10° when machining high-speed plates is 4.1%, and the wear amount at 20° reaches 17.1%. Changing the secondary face angle has no significant effect on the drilling characteristics. When designing the tool structure, increasing the drill point angle and reducing the primary face angle appropriately can improve the processing quality.

TiAlN-based coatings are prepared on the three commonly used micro drills and rods with different sizes by multi-arc ion plating. The coatings with different thickness ranging from 2.1±0.3 μm to 8.6±0.3 μm are fabricated by adjusting the deposition time. The effects of coating thickness on the stiffness of micro drills and rods and the holes position accuracy by micro drills are studied. The results show that the best adhesion level of HF1-HF2 for coatings with different thickness is obtained. The bending test reveals that the bending deviation of three sizes of micro drills and rods decreases gradually with the increase of coating thickness, and the corresponding stiffness increases gradually. As the coating thickness on the micro drills of φ0.15~3.0 mm increases to 6.37 μm, the stiffness is 25.7% higher than that of uncoated ones. Similarly, the stiffness increases by 23.1 % and 15.6 %, respectively, with the increase of the coating thickness to 8.6±0.3 μm on the micro drills of φ0.20~4.5 mm and φ0.25~5.5 mm. The drilling test shows that the holes position accuracy of Cpk value by the coated micro drills is higher than that of uncoated micro drills. The holes position accuracy can be further improved by grinding the bits of the micro drills.

Cemented carbide is well known as the "industrial tooth", which is predominantly composed of strategic precious metals such as tungsten, cobalt and nickel. It would be of great significance to efficiently realize the recycling of cemented carbide. Roll ring is an essential material for the rolling of rebar, and is also one of the most important applications for cemented carbide. Roll rings mainly consist of coarse-grained tungsten carbide, cobalt and nickel. In order to develop a cost-effective recycling method for cemented carbide ring, the high-temperature recovery of scrapped cemented carbide roll is explored in this paper. The recovered powder is reused as raw materials for manufacturing cemented carbide rings, which have undergone the measurement of physicochemical propertiesand practical application. It is found that the bending strength and fracture toughness of the prepared cemented carbide ring by the high-temperature recycled powder are only slightly worse than that of the standard ring, and after passing through the same amount of steel to be rolled, the surface roughness in grinding is only slightly larger than that of the original cemented carbide ring, which proves that the recycling of scrapped cemented carbide ring based on the high temperature recovery method is technologically feasible.

Molybdenum based alloy withsmall amount of titanium, zirconium or tantalum addition has high strength and toughness, which is widely used in high-end medical, nuclear power, aerospace, sputtering target and other fields. The  analysis of titanium, tantalum and zirconium is usually performed by traditional chemical methods with long cycle and low efficiency. In this paper, inductively coupled plasma spectrometer was used to establish the analysis method through the investigation of sample dissolution, analysis line selection and matrix interference analysis. Results show that the correlation coefficients of calibration curves are 0.999 in the range of Ti mass fraction from 0.003 0% to 8.00%, 0.999 in the range of Ta mass fraction from 0.025% to 1.00%, and 0.999 in the range of Zr mass fraction from 0.008 0% to 1.00%. The relative standard deviations (RSD) of Ti, Ta and Zr are 1.68%, 2.20% and 3.51%, respectively. The recoveries of Ti, Ta and Zr are 99.6%- 104%, 98.8%- 110% and 98.8%- 110%, respectively.The analysis results are consiste001nt with the chemical method, which greatly improves the analysis efficiency and meets the requirements of quality control.

High purity tungsten is widely used in sputtering targets, discharge lamp electrodes and high temperature furnace components because of its excellent properties of high electron migration resistance, high hardness and high melting point. In this paper, the impurity removal methods and trace impurity detection methods of high-purity tungsten are summarized. The principles, advantages, disadvantages and application status of wet impurity removal methods (precipitation method, ammonia crystallization method, solvent extraction method, and ion exchange method) and fire impurity removal methods (electron beam melting method, regional melting method, and chemical vapor deposition) of high-purity tungsten are emphatically introduced. At last, several key problems to be solved in the future impurity removal methods of high-purity tungsten are pointed out, so as to provide theoretical and technical support for the design of efficient and reasonable impurity removal schemes.

Nitinol has become an ideal human implant material due to its shape memory effect and good biocompatibility, and is widely used in medical fields such as human luminal stents. Fatigue performance is an important index for medical applications of this alloy, and it needs to meet a fatigue life of more than 10 years. In this article the relevant research on the fatigue performance of nickel-titanium alloys has been comprehensively reviewed, including predicting the fatigue life of the alloy by finite element analysis, using surface treatment technology and heat treatment technology to improve the corrosion resistance and wear resistance of the alloy, thereby improving the fatigue performance of the alloy. On this basis, it is proposed to adjust the chemical composition, processing technology, heat treatment method and alloy surface modification of Nitinol to improve the biocompatibility and fatigue resistance of Nitinol, which will become a research hotspot of Nitinol.

The development of WC-Co cemented carbide with high strength and toughness was briefly described in the present article. A recent developed milling method named as plasma milling and its basic principle were also introduced. And then, the application of "synchronous carbonization and sintering method" based on the plasma milling technology in the preparation of high-performance WC-Co cemented carbide was summarized in the paper. There are three advantages in the preparation of cemented carbide by plasma milling: (1) The reaction activity of W and C is greatly improved, and the synthesis temperature of WC is greatly reduced, which makes it possible to prepare WC-Co cemented carbide through "synchronous carbonization and sintering method", simplifies the preparation process and realizes energy saving and consumption  reduction. (2) Plasma milling is beneficial to form plate-like structured WC grains and control the morphology of WC, which creates a large space for the design and control of the microstructure of WC-Co cemented carbide. (3) Plasma milling is suitable for large-scale production of WC-Co cemented carbide through common sintering, and the obtained WC-Co alloy has a good combination of strength and toughness.

Due to its excellent wear resistance and corrosion resistance, cemented carbide is widely used in many fields. 3D printing, also known as “additive manufacturing”, is an emerging advanced molding technology which has been applied in aerospace, bio-materials and other fields. However, in the field of refractory metals and their carbides, such as cemented carbide, it is still in its infancy. Some companies and institutes are working on or paying attention to the development of 3D printed cemented carbide, but so far, there is still no substantial progress. It means that there is no 3D printing method can comprehensively solve all the problems such as poor surface, microscopic porosity and low strength etc. of cemented carbide printing products. In this paper, the characteristics and also problems of 3D printing methods for cemented carbide, such as SLS/SLM, FFF, BJP and DLP etc. in domestic and foreign countries in recent years has been organized, discussed and analyzed, and the development of 3D printing technology for cemented carbide is prospected.

In this study, Ti(C,N)-WC-NbC-Co-Ni cermets with different ZrC additions were fabricated. The influences of ZrC addition on microstructure, mechanical properties and corrosion resistance in 2 mol/L HCl solution were explored. The experimental results demonstrate that with moderate ZrC addition the synergistic effect between ZrC and NbC can inhibit the precipitation of brittle rim phase and increase Nb content in the binder, which endows cermets better mechanical properties and corrosion resistance. When the addition of ZrC is up to 10% (mass fraction), a great change in the microstructure of cermet has been observed. The Ti(C,N) particles and Nb content in the binder decrease obviously, meanwhile white core-grey rim structures are formed, which results in the decline of mechanical properties and corrosion resistance. The cermet with 1%ZrC (mass fraction) possesses transverse rupture strength of 2 549 MPa and the highest fracture toughness of 13.0 MPa·m^1/2.

The Mo₂FeB₂ based cermets with different Ni content were prepared by reaction sintering process. The effect of Ni addition on the microstructure and mechanical properties of the Mo₂FeB₂ based cermets was studied by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The experimental results show that the Ni addition occurs in the binder phase and hard phase. Although the Ni addition has no obvious effect on the microstructure, the transverse rupture strength (TRS) is significantly increased from 1 750 MPa to 2 200 MPa. The results of the first principle calculations show that the Mo₂(Fe,Ni)B₂ phase has a relatively higher plasticity and lower hardness compared with that of the Mo₂FeB₂ phase.

Compared with WC-Co, functionally graded cemented carbide (FG WC-Co) can provide excellent combination of hardness and fracture toughness. Based on the driving force of cobalt and carbon that liquid-Co migrates from higher Co content to lower one, from higher C content to lower one, bilayered samples of WC-15%Co with carbon-rich and high-cobalt layer and WC-6%Co with carbon-depleted low-cobalt layer were designed. The microstructure and mechanical properties of the bilayered cemented carbide were studied by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that the Co phase in the bilayered samples migrates from a carbon-rich and high-cobalt layer to a carbon-depleted and low-cobalt layer to form a gradient structure, in addition, as the difference in C content between the two layers decreases, the gradient of Co concentration becomes larger; the WC grain size in the high cobalt layer is larger than that in the low cobalt layer, besides, as the difference in C content between the two layers decreases, the difference in WC grain size becomes larger; as the difference in C content between the two layers decreases, the magnetic coercivity (Hc) becomes smaller and the cobalt magnetic (Com) becomes larger; the hardness gradually increases from 1 260 HV to 1 408 HV, the TRS of 2 612 MPa measured from WC-15%Co is higher than that of 2 388 MPa measured from WC-6%Co.

The WC-6%Co cemented carbide samples were prepared by the same process with type 08 WC powder produced by three different manufacturers as raw materials. Based on the detailed analysis of impurity content, particle size, phase composition, micro-morphology, grain size and lattice parameters of the raw powder, and characterization of the microstructure, number of abnormal growth WC grains and mean WC grain size of the alloys at different sintering temperatures, the influence of the characteristics of WC powders on the sintering sensitivity of the alloys was studied. The results show that by using WC-C powder with uniform particle size distribution, large grain size, complete crystallinity and small difference between lattice constant and its standard value as raw materials, it can effectively reduce the sintering sensitivity of the alloy. When the sintering temperature increases from 1 410 ℃ to 1 450 ℃, the amount of abnormal growth WC grains in the alloy produced by WC-C powder has a small increase and the mean WC grain size has no obvious change, which is maintained at 0.48 μm. At the same time, when carbon content of WC fluctuates from 6.17% to 6.21%, its influence on the amount of abnormal growth WC in the alloys is relatively small.