Four types of hollow spherical micro- and nano-szied powders of ZrO2-7wt.%Y2O3(7YSZ), ZrO2-7wt.%Y2O3, Al2O3-13 wt.% TiO2(AT) and WC as well as one type of core/shell structured powder of ZrB2-30 wt.%Mo Si2 were prepared via plasma processing. In addition, the formation mechanisms of hollow spherical and core/shell structured powders prepared via plasma processing were also proposed.
In the present study,WB_2(N) films are fabricated on silicon and YG8 substrates at different N_2 pressures by reactive magnetron sputtering.The influence of N_2 partial pressure(P_(N2)) on the film microstructure and characteristics is studied systematically,including the chemical composition,crystalline structure,residual stress,surface roughness as well as the surface and the cross-section morphology.Meanwhile,nano-indentation and ball-on-disk tribometer are performed to analyze the mechanical and tribological properties of the films.The results show that the addition of nitrogen apparently leads to the change of the structure from(1 0 1) to(0 0 1) orientation then to the amorphous structure with the formation of BN phase.And the addition of nitrogen can greatly refine the grain size and microstructure of the films.Furthermore,the residual stress of the film is also found to change from tensile to compressive stress as a function of P_(N2),and the compressive stress increases with P_(N2),The WB_2(N) films with small nitrogen content,which are deposited at P_(N2) of 0.004 and 0.006 Pa,exhibit better mechanical,tribological and corrosion properties than those of other films.Further increase of nitrogen content accelerates the formation of BN phase and fast decreases the film hardness.In addition,the large N_2 partial pressure gives rise to the target poisoning accompanied by the increase of the target voltage and the decrease of the deposition rate.
采用大气等离子喷涂分别以抛光的316L不锈钢和抛光的Ni Co Cr Al YTa涂层为基体依次进行7%氧化钇稳定氧化锆(7%Y2O3-Zr O2,7YSZ)粒子收集。首先研究了不同基体温度对7YSZ粒子铺展形貌的影响,其次原位观察不同基体与铺展粒子的结合形貌,使用了聚焦离子束focused ion beam进行切割;最后为进一步解释沉积粒子与不同基体的界面结合情况,采用了有限元软件ANSYS/LS-DYNA对7YSZ粒子沉积过程进行模拟。结果表明:不同类型基体的基体温度控制在250℃左右时均能获得圆盘状扁平7YSZ粒子。圆盘粒子在316L基体上铺展时边沿区域有翘曲现象,而中心区域则与基体结合紧密;圆盘粒子在Ni Co Cr Al YTa涂层基体上铺展时边沿没有翘曲现象,整个扁平粒子与基体结合紧密。另外,7YSZ粒子在2种基体上的铺展形貌ANSYS模拟结果与实际粒子沉积形貌一致。
As potential thermal barrier coating(TBC)materials,Ruddlesden—Popper structured BaLn_2Ti_3O_(10)(Ln=rare earth)compounds possess excellent phase stability and desirable thermo-physical properties as well as interesting anisotropic structure.In this paper,the effects of pressure during BaLa_2Ti_30_(10)(BLT)bulk preparation on the grain orientation were investigated.BLT grains exhibited lamellar structure,but the grain orientation depended strongly on the existence of pressure during bulk preparation.When pressure was applied,BLT grains preferentially grew along pressing direction,leading to formation of the texture parallel to pressing direction,but BLT grain orientation became relatively random when pressure was absent.However,in the small scale area,BLT grains grew preferentially along c-axis with independence on pressure during preparation.Pressure affected BLT grain orientation at the rapid growth stage according to the grain growth model of BLT.
Xizhong WangLei GuoHongbo GuoGuohui MaShengkai Gong
In this study,CrN/Cr_2O_3 double-layered coatings with various thickness ratios of CrN vs Cr_2O_3 layer were prepared by arc ion plating technology.The influences of the thickness ratio of CrN vs Cr_2O_3 layer on the microstructural characteristics as well as the mechanical and tribological properties of the CrN/Cr_2O_3 doublelayered coatings were investigated.The corresponding mechanisms were also discussed.The results indicated that the insertion of CrN layer between the Cr_2O_3 layer and substrate can effectively decrease the internal stress level of the coating.With increasing the thickness ratio of CrN vs Cr_2O_3 layer,the surface roughness of double-layered coatings decreased gradually,which had a certain influence on the friction coefficient.In addition,the microhardness also declined gradually,the adhesive strength almost increased linearly,whereas the wear rate declined firstly and then increased slightly.As the thickness ratio was 2:1,the double-layered coating exhibited the best wear resistance.
Chang-Ming ShiTie-Gang WangZhi-Liang PeiJun GongChao Sun
