Study On The Technology And Performance Of Medical Titanium Selective Laser Melting And Surface Cladding Titanium Tantalum Coating

Titanium and titanium alloys are more and more widely used in medicine.Pure titanium has no physiological toxicity and good biocompatibility,and can be used as a material of choice for oral implants and human bone implants.However,pure titanium has the disadvantages of low hardness,poor wear resistance and poor corrosion resistance.It is prone to loosening and corrosion-induced failures after implantation in the human body,which affects the long-term stability of the implant.At the same time,the pure titanium formed by the traditional process can not meet the personalized needs of the human body,which greatly limits the wide application of pure titanium in biomedicine.In this paper,the performance of domestic pure titanium as a matrix material by selective laser melting technology was compared with that of traditional as-cast pure titanium and imported SLM pure titanium.Then TiTa alloy coating was prepared on the SLM pure titanium substrate by laser cladding technology,and the coating materials,cladding process and coating properties were studied.?1?In this paper,the domestic pure titanium samples were formed by the selected laser melting technology on the German TRUMPF equipment model Truprint1000.Orthogonal experiments were used to optimize the process parameters of SLM pure titanium,resulting in shaped parts with a density of more than 99.5%.By testing the structure and properties of the upper and side surfaces of the shaped sample under the optimal process,it was found that the upper surface structure was fine strip martensite and the side surface was needle martensite.The upper surface hardness,wear resistance and corrosion resistance were better than the side surfaces.Compared with traditional as-cast and SLM imported pure titanium,it was found that in terms of tensile properties,SLM domestically produced pure titanium fully complies with national standards,was superior to pure titanium prepared by traditional processes,and was not much different from imported pure titanium.?2?Using SLM pure titanium as the substrate,Ti20Ta alloy cladding layer was prepared on the surface by laser cladding technology.The effects of laser power P,scanning speed V and powder thickness d on the surface morphology of TiTa alloy coating were investigated.The cross-sectional parameters of the cladding layer under different processes were measured and calculated:cladding layer height H,width b,molten pool depth h and dilution rate?.The results showed that with the increase P,the surface of the cladding layer tended to be flat and smooth.H was negatively correlated with P,and b,?and h were positively correlated with P.When P increased from 900W to 2100W,H decreased by 0.08mm,b,?and h increased by 2.001mm,26.32%,0.26mm.Compared with other scanning speeds,the morphology of the cladding layer surface was the best at a scanning speed of 7 mm/s.The change trend of the cross-sectional size with V was exactly opposite to the laser power.When V was 11mm,H was 0.772mm at the maximum,and b,?and h were the smallest 3.68mm,1.53%,0.012mm.When coating thickness d increased from 1mm to 3mm,the surface of the cladding layer gradually lost its metallic luster,and H increased from 0.742mm to 2.770mm,while b reduced from 3.712mm to3.412mm.when d was 3mm,h and?were both the smallest 0.It was observed through CT scanning that the single-pass cladding layer had more unmelted powder from near the center to the edge.The single-pass cladding layer had more unmelted powder in the early stage of laser scanning than in the later stage of laser scanning.?3?The effect of Ta content on the microstructure and properties of laser cladding TiTa alloy cladding layer was studied.The results showed that as the tantalum content increased from10wt%to 30wt%,the height and width of the cladding layer decreased by 0.015mm and0.14mm,the molten pool depth increased by 0.009mm,and the dilution rate increased by 1.17%.The XRD and microstructure analysis showed that the titanium-tantalum cladding layer was mainly composed of needle-shaped martensite.In addition to the needle-shaped martensite phase,a significant increase in the equiaxed?phase content was observed in the Ti30Ta alloy cladding layer.In addition,the hardness of the cladding layer was significantly higher than that of the substrate.With the increase of tantalum content,the hardness,wear resistance and corrosion resistance of the cladding layer gradually improved.The microhardness value of the Ti30Ta alloy cladding layer reached 432HV;the optimal performance was about twice that of the substrate;the corrosion current density was 2.024×10^-8 A/cm²,which was about an order of magnitude smaller than the substrate?9.556×10^-77 A/cm²?.