Study On Process And Friction And Wear Properties Of Salt Bath Compound Treatment On Ti6Al4V

Ti6Al4V alloy is widely used in the field of medical artificial joint because of its excellent performance,which is the most widely used medical titanium alloy material.However,the poor friction and wear properties of Ti6Al4 V alloy seriously hindered its further application in artificial biological substitute materials.However,the poor friction and wear properties of Ti6Al4 V alloy seriously hindered its further application in artificial biological substitute materials.In this paper,Ti6Al4 V alloy is treated by salt bath compound treatment and the orthogonal test is designed with hardness as the evaluation index to obtain the typical process parameters of salt bath compound treatment.And the Ti6Al4 V alloy is treated by salt bath compound treatment under the typical process parameters.The microstructure of the Salt bath composite samples carburized layer was analyzed and the surface hardness,roughness,wettability,friction and wear resistance and corrosion resistance of three contrasting samples,whichare the salt bath composite treatment sample,the nitrided sample and the original sample,are studied.And the orthogonal experiment was carried out with the wear volume,friction coefficient and corrosion rate as the evaluation indexes tooptimise the salt bath composite processing parameters and obtain the optimum process parameters.And the specific test results are as follows:(1)The typical process parametersobtained by orthogonal test are:nitriding for 4h at 580?,oxidating for 20 min at 400?.The infiltrated layer of salt bath compound treatment sample mainly includes Ti8C5 phase,TiCN phase,TiO2 phase and Ti3 O phase.Aftersalt bath compound treatment,the infiltrated layerfrom outside to insideisoxide layer,loose layer,compound layer and diffusion layer in turn.And the thicknesses of each layer are:5?moxide layer,5~15?mloose and compound layer,10?mdiffusion layer.The surface roughnessvalue of thecompoundtreatment sample is0.325?m,which is reduced by 70.8% comparing withthe original sample.And the surface hardness is 710.8HV,which is 1.92 times that of original sample.The hardness curves of composite treatmentfirstly increase and then decrease.And with the increasing of temperature,the infiltration amount of C and N will increase and the loose layer will be more serious,which makes the maximumhardness position move inward.(2)The friction and wear resistance of the compositetreatment samples,which have better friction and wear stability,are better than the original and nitrided samples.The load has a great influence on the friction and wear properties of the original and nitrided samples,and has little effect on the friction and wear properties of the composite samples.And sliding frequency has a great influence on the friction coefficient of the alloy,andhas little influence on the wear resistance.In addition,the lubrication condition has a great influence on the friction and wear properties of the samples and thelubrication effect of calf serum was better than that of normal saline.Under the condition of normal saline lubrication,the friction reducing effect of the nitrided sample and salt bath composite sample is not ideal.And in the salt bath compound treatment processes,the most influential factor on wear volume is oxidation temperature.The best process parameters of the minimum wear volume are: nitriding for 1.5h at 610?,oxidating for 40 min at 400?.And the minimum wear volume is 1.11 mg,which is reduced by69.5% comparing withthe original sample.In the salt bath compound treatment processes,the most influential factor on friction coefficient is nitriding temperature.Andthe best process parameters of the minimum friction coefficient are: nitriding for 3.5h at 580?,oxidating for 40 min at 400?.And the minimum friction coefficient is 0.2467,which is reduced by42.1% comparing withthe original samples.(3)The corrosion resistance of the sample can be improved significantly by the salt bath treatment and that of the nitrided sample decreases.Among all the factors of the salt bath composite treatment processes,the nitriding temperature has the greatest influence on the corrosion rate.The optimum process parameters for obtaining the minimum corrosion rate are:nitriding for 1.5h at 610?,oxidating for 40 min at 400?.And the minimum corrosion rate is0.4793×10-3g·m-2·h-1,which isreduced by65.7% comparing withthe original samples.The effect of nitriding treatment on the surface wettability of Ti6Al4 V sample is better than that of salt bath compound treatment.And the salt bath compound treatment sample has better biocompatibility,which ismore suitable for cell adsorption.