Study On The Technology And Properties Of Ni-TiB₂ Cermet By Selective Laser Melting

Ceramic reinforced metal matrix composites have both excellent ductility and electrical conductivity of metal materials,and outstanding hardness and wear resistance properties of ceramic.Therefore,metal matrix composites have attracted widespread attention.In this paper,TiB₂/Ni composites?0vol.%,5vol.%,10vol.%,15vol.%?were successfully prepared using selective laser melting?SLM?process.First,the SLM forming process of metallic nickel was studied.The relationship between the line energy density of laser and the shape of the melt path was analyzed.Based on the above results,metallic Ni blocks were then prepared-the surface morphology,density,microstructure evolution and tensile properties of which were characterized.The results presented that the metallic nickel blocks have optimal properties at laser power of 215W,scanning speed of960mm/s,and hatch distance of 0.11mm.The corresponding roughness,density,tensile strength,yield strength and average elongation were 10.5?m,99.6%,420MPa,345MPa and 31%,respectively.The fracture was ductile fracture.Secondly,the forming process of TiB₂/Ni composites using SLM technology was also studied.It was founded that the relative density decreased gradually with the increase of TiB₂.Meanwhile,the relative density increased first and then decreased with the increasing of laser line energy density.In addition,the forming quality of X-Y surface was better than the one of Y-Z surface.When the laser line energy density was 215J/m,the surface roughness and relative density of Ni-5vol.%TiB₂ composites were 13.04?m and 99.13%,respectively.And the X-Y and Y-Z section had the lowest porosity of 0.30%and 1.49%,correspondingly.Finally,the wear properties and hardness of TiB₂/Ni composites were studied.The results showed that the TiB₂ volume fraction had a more obvious on the wear properties than the laser line energy density.The results presented that Ni-5vol.%TiB₂ composites had better mechanical properties at laser power of 140W,scanning speed of 650mm/s,and hatch distance of 0.11mm.Its Vickers hardness of the X-Y and Y-Z plane were 354.92HV_0.2 and 349.37HV_0.2,respectively.Moreover,the Vickers hardness of X-Y and Y-Z surfaces of Ni-10vol.%TiB₂ composites were548.47HV_0.2 and 525.69HV_0.2,respectively,and its hardness was 3.32 times that of Nickel.The friction coefficient and wear rate of Ni-5vol.%TiB₂ composites were 0.4511 and 8.361?10^-6mm³N^-1m^-1 which was 90%lower than pure Ni.The wear profile width and area were 1.167?m and 471.585?m²,respectively.