WC-10Co-4Cr coatings were prepared on 45#steel by plasma spraying(APS),supersonic plasma spraying(SAPS)and high velocity oxy-fuel thermal spraying(HVOF),respectively.The porosity,microhardness,and wear resistance of the three coatings were analyzed and compared.The results show that the two coatings prepared by SAPS and HVOF have similar performance and single phase composition similar to the powders.Compared with the coating prepared by APS,the two coatings prepared by SAPS and HVOF have higher density and microhardness and better wear resistance.

Different amounts of WC was added to the ternary boride Mo2FeB2-based cermet and then vacuum liquid phase sintering was carried out.The sintered samples were characterized.The results show that WC addition doesn't affect the in-situ liquid phase reaction process to generate the ternary boride Mo2FeB2.WC can be the nucleation center of Mo2FeB2 particle to promote material densification during sintering.WC particles and Mo2FeB2 particles well combine to form dual hard phase,dispersing in Fe-based binder phase and effectively enhancing hardness and wear resistance of the Mo2FeB2-based cermet.When mass fraction of the added WC is 20%,the sintered sample has the highest hardness of HRA87.9improved by 7.2%,and the best wear resistance increased by 10 times under the experimental conditions of wheel grinding.

Ti(C,N)-xWC-Ni-Mo-C cermets with different WC contents were prepared by powder metallurgy.Microstructure,fracture morphology and crack propagation path were analyzed by SEM.The results show that the cermets contain black core-gray rim microstructure,as well as white core-gray rim microstructure.The grains are refined with appropriate WC addition,while the grains grow up with 20% WC.The main fracture models of the cermets are intergranular fracture and transgranular fracture.Crack bridging,crack deflection and microcrack occur during crack propagation.

TiC-TiB2 composite ceramics with different Cr content were prepared by combustion synthesis in high gravity field using Ti+B4C as the primary reactive system assisted by different contents of CrO3+Al as the enhancement system.XRD,FESEM and EDS results show that the prepared composite ceramics are mainly composed of many fine TiB2 platelet grains and TiC spherical grains,and most Cr-rich metal phase intertwines with TiB2 platelet grains.With the content of CrO3+Al increased,system adiabatic temperature rises,and volume fraction of Cr-rich metal phase in TiC-TiB2 composite ceramic increases.It is supposed that Ti-Cr-C-B alloy liquid is the product of combustion reaction in high gravity field.During cooling and solidification of the alloy liquid,TiC nucleates and precipitates at first and then TiB2 precipitates.Finally,Cr and a small amount of unreacted Ti precipitate to fill the shrinkage cavity in the skeletal structure of TiB2 platelet grains and thereby increase the density of TiC-TiB2 composite ceramics.

The Ti2 SnC material was prepared by self-propagation high-temperature synthesis(SHS)with2Ti/Sn/C and Ti/Sn/TiC as the raw materials.Effects of the two raw materials on Ti2SnC synthesis were investigated.The results show that with the two raw materials,Ti2 SnC can be synthesized by SHS,and the products contain a small amount of TiC and Sn.With 2Ti/Sn/C as the raw powder material,the synthesized Ti2 SnC has well-developed lath grains of about 10μm length and about 2μm width.With Ti/Sn/TiC as the raw material,the synthesized Ti2 SnC has fine granular grains of about 1~5μm granularity.

The molybdenum powders were put into the tube and heated to 500℃,and then two pass A-route equal channel angular pressing(ECAP)or hot pressing experiments were carried out.Particle morphology,pore distribution and microhardness were compared of the molybdenum powders from different pressing methods.The results show that after two pass ECAP,pore distribution of the sample is more uniform,and both particle deformation degree and microhardness are higher.After hot pressing,pore distribution of the sample is nonuniform,its density at the upper end is higher than that at the down end,and its particle deformation degree is small.During hot pressing,pressing force cannot result in brittle fracture of the particles,so the sample has lower microhardness than the sample processed by equal channel angular pressing.

The microstructure was studied of AlFeCrCoCu high-entropy alloy prepared by vacuum arc melting.Effects were investigated of tempering process on alloy microstructure,hardness and corrosion resistance in 3.5% NaCl solution.The results show that the alloy has dendrite microstructure,the dendrite is Al,Fe,Cr,Co-rich BCC phase and intergranular microstructure is Cu-rich FCC phase.Alloy melting point is about 1 380 ℃,and intergranular Cu-rich phase begins phase transition at about 1 050 ℃.With the increase of tempering temperature,the grains begin to grow up until develop into coarse grains at about 1 000℃.The alloy exhibits a superior resistance to temper softening.Electrochemical test results show that the alloy has better corrosion resistance than 304 stainless steel,and 800 ℃ temper microstructure has the highest corrosion resistance.

AB3-typed hydrogen storage alloy(Mm0.78Mg0.22Ni2.48 Mn0.09Al0.23Co0.47,Mm=82.3%La+17.7%Nd)was modified by electroless nickel plating to improve its electrochemical and kinetic properties.Alloy phase composition was analyzed by XRD,and the results show that the phase composition of the alloy has no change after electroless nickel plating.Electrochemical test results show that the alloy electrode has significantly increased discharge specific capacity after electroless nickel plating with the maximum327.7mA·h/g,and its cycle stability is also greatly improved with increased capacity retention rate from original 83.3% to 93.3% after 50charge/discharge cycles.Electroless nickel plating can improve alloy electrochemical properties,and thereby exchange current density i0,limiting current density iL,corrosion potential Ecorrand electrochemical reactivity of the alloy electrode are significantly improved.

Selective reduction was studied of nitrogen oxides on AgO/Al2O3 catalyst prepared by impregnation and hydrothermal coprecipitation.The results show that preparation methods of the catalyst play an important role in its catalytic effect.Prepared by hydrothermal coprecipitation,AgO/Al2O3 catalyst is more active than that by impregnation.The catalyst systems with different reducing agents have different reduction performance.AgO/Al2O3 catalyst prepared by hydrothermal coprecipitation has better water and sulfur resistance and high selective reduction activity due to strong interaction between AgO and high specific surface area Al2O3.Oxygen adsorbed on the catalyst surface greatly promotes selective oxidation of nitrogen oxides.

Based on the formation mechanism of milling defects of carbon fiber-reinforced composite,the idea was proposed of staggered upper and lower cutting edges of cemented carbide end mills,and a newtype end mill was designed.Experiments were carried out of milling carbon fiber-reinforced composite with the new-type staggered-edge end mill and a standard cemented carbide end mill,and then milling performance of the new-type end mill was evaluated.The results show that the new-type cemented carbide staggered-edge end mill is more suitable for milling of carbon fiber-reinforced composite with less milling defects,better machined surface quality and longer tool life.