Titanium nitride(TiN), characterized by its high hardness and strength, was widely used as ceramic coating to improve the wear resistance of matrix materials. In this work, AlCrFeNiTi_(x) high-entropy alloy(HEA) powde...Titanium nitride(TiN), characterized by its high hardness and strength, was widely used as ceramic coating to improve the wear resistance of matrix materials. In this work, AlCrFeNiTi_(x) high-entropy alloy(HEA) powders were synthesized by direct electrochemical reduction in molten salt from the mixed metal oxides. Then,TiN ceramic coating on the AlCrFeNiTi_x bulk HEA containing the topologically close-packed(TCP) phase(σphase, Laves phase, and Ti_(3)Al phase) was prepared by vacuum hot pressing sintering, where nitride element come from boron nitride parting agent sprayed on the graphite mold. The effect of titanium content on the crystal structure, microstructure, hardness, and wear resistance of the products were investigated by X-ray diffraction, field emission scanning electron microscope, field emission electron-probe microanalysis,Vickers hardness tester, and friction–abrasion testing machine. The bulk HEAs exhibit excellent hardness and its hardness increases significantly with the increase of titanium content. The wear mechanism changes from both of predominantly delamination and accompanied oxidative wear to single delamination wear,which is due to ultra-high melting point and high hot hardness of TiN, that can effectively prevent the oxidation and deformation of the worn surface. Formation of the ceramic coatings containing the TiN second phase and TCP phase are the key factor to AlCrFeNiTi_x alloy with the excellent hardness and wear properties.展开更多
Gr/CuCr10 alloys with graphene contents of 0.1 wt.%,0.3 wt.%,0.5 wt.%,and 0.7 wt.%were prepared by a hot pressing sintering process.Compared with CuCr10 alloy,the relative density of CuCr10 composite with 0.3 wt.%addi...Gr/CuCr10 alloys with graphene contents of 0.1 wt.%,0.3 wt.%,0.5 wt.%,and 0.7 wt.%were prepared by a hot pressing sintering process.Compared with CuCr10 alloy,the relative density of CuCr10 composite with 0.3 wt.%addition of graphene remained constant,while the electrical conductivity increased from 62.2%(IACS)to 69.5%(IACS).The main reason for the increased electrical conductivity is that the addition of graphene leads to the size reduction of Cr phase and thus reduces the scattering of electrons.In addition,Brinell’s hardness of 0.3 wt.%Gr/CuCr10 composite increased from HB 91.8 to HB 99.6 compared with that of CuCr10 alloy.The graphene was mainly distributed at the interface of Cu and Cr.A nano-Cr;C;phase,which has been observed through HRTEM,is the main reason for the wettability enhancement at the interface of Cu and Cr,thus improving the hardness of the material.展开更多
基金supported by the National Natural Science Foundation of China (52174299)the Chongqing Key Laboratory of Vanadium-Titanium Metallurgy and New Materials, Chongqing University, Chongqing 400044, China。
文摘Titanium nitride(TiN), characterized by its high hardness and strength, was widely used as ceramic coating to improve the wear resistance of matrix materials. In this work, AlCrFeNiTi_(x) high-entropy alloy(HEA) powders were synthesized by direct electrochemical reduction in molten salt from the mixed metal oxides. Then,TiN ceramic coating on the AlCrFeNiTi_x bulk HEA containing the topologically close-packed(TCP) phase(σphase, Laves phase, and Ti_(3)Al phase) was prepared by vacuum hot pressing sintering, where nitride element come from boron nitride parting agent sprayed on the graphite mold. The effect of titanium content on the crystal structure, microstructure, hardness, and wear resistance of the products were investigated by X-ray diffraction, field emission scanning electron microscope, field emission electron-probe microanalysis,Vickers hardness tester, and friction–abrasion testing machine. The bulk HEAs exhibit excellent hardness and its hardness increases significantly with the increase of titanium content. The wear mechanism changes from both of predominantly delamination and accompanied oxidative wear to single delamination wear,which is due to ultra-high melting point and high hot hardness of TiN, that can effectively prevent the oxidation and deformation of the worn surface. Formation of the ceramic coatings containing the TiN second phase and TCP phase are the key factor to AlCrFeNiTi_x alloy with the excellent hardness and wear properties.
基金financially supported by the National Natural Science Foundation of China(No.51871111)Jinan Changan Graphene Aluminum Material Technology Co.,Ltd.,Chinathe Dingmei New Material Technology Co.,Ltd.,China。
文摘Gr/CuCr10 alloys with graphene contents of 0.1 wt.%,0.3 wt.%,0.5 wt.%,and 0.7 wt.%were prepared by a hot pressing sintering process.Compared with CuCr10 alloy,the relative density of CuCr10 composite with 0.3 wt.%addition of graphene remained constant,while the electrical conductivity increased from 62.2%(IACS)to 69.5%(IACS).The main reason for the increased electrical conductivity is that the addition of graphene leads to the size reduction of Cr phase and thus reduces the scattering of electrons.In addition,Brinell’s hardness of 0.3 wt.%Gr/CuCr10 composite increased from HB 91.8 to HB 99.6 compared with that of CuCr10 alloy.The graphene was mainly distributed at the interface of Cu and Cr.A nano-Cr;C;phase,which has been observed through HRTEM,is the main reason for the wettability enhancement at the interface of Cu and Cr,thus improving the hardness of the material.
