Research On Low Temperature Plasma Nitriding And Properties Of 316L Stainless Steel

AISI316L stainless steel has excellent corrosion resistance,biocompatibility,high toughness and plasticity,and is widely used in all walks of life.AISI 316L stainless steel has low hardness,poor wear resistance,and cannot be hardened by phase change strengthening,and cannot be hardened by traditional quenching,tempering and other technologies,which affects the service life of stainless steel parts and limits the play of material properties.Low-temperature plasma nitriding produces plasma by glow discharge.Under the action of strong electric field of the plasma,high speed nitrogen and hydrogen ions bombard the surface of the workpiece and infiltrate the active nitrogen atoms into the material.Nitrogen compounds can be formed by nitrogen infiltration into the material,which has high hardness,thermal stability and dispersion,so the mechanical properties of the material will be greatly improved.At the same time,low temperature plasma nitriding has the characteristics of short cycle,low brittleness of nitriding layer,controllable thickness and structure of nitriding layer,and the function of purifying surface.In this paper,the surface of AISI316L austenitic stainless steel was treated with low temperature plasma nitriding technology to study the effect of specific surface area on the microstructure,wear resistance and corrosion resistance of low temperature glow plasma nitriding layer of AISI316L austenitic stainless steel.Results show that:after380?low temperature glow plasma nitriding treatment after 12h,AISI316L stainless steel specimen surface nitriding layer,metallography and EPMA analysis,outer diameter of the same circle,when the specific surface area of 0.3cm²kg^-1,N elements in nitriding layer of sample after nitriding uniform distribution,no obvious enrichment,the surface of N elements,most closer to substrate,N the lower element content,decrease distribution of nitriding layer in Cr element present decreasing distribution,but is not so steep decrease N elements.cm²kg^-1 when the specific surface area increases to 0.7,the permeability layer thickness than 13?m thicker than the sample surface area0.3 cm²kg^-1,and there are obvious precipitates,the uneven distribution of N elements,in the hard phase,and the distribution of N elements rarely have obvious Fe element enrichment instead,enrichment regions of clusters,12h after glow plasma nitriding treatment at low temperature,low temperature nitriding specimen hardness after 1015HV_0.05,1080 HV_0.05,respectively HV_0.05,improve the surface hardness of 316L austenitic stainless steel,The hardness of the nitriding sample was increased by 4⁵times compared with that of the unnitriding sample.The larger the specific surface area of the AISI316L austenitic stainless steel sample,the thicker the nitriding layer,the higher the surface hardness,the lower the friction coefficient,the better the wear resistance and the smaller the specific wear rate.The pitting potential of AISI316L matrix was-0.4115V_SCE,and the corresponding corrosion current was 3.196�10^-6A/cm².With the increase of specific surface area,the pitting potential of samples after low-temperature nitrification treatment decreased to-0.4683V_SCE,-0.4532V_SCE,-0.4272V_SCE,respectively.The corresponding corrosion currents were 6.656�10^-6 A/cm²,5.534�10^-6 A/cm²,and 3.773�10^-6 A/cm²,respectively.After low temperature nitriding treatment,pitting potential decreased slightly compared with AISI316L matrix,but basically remained at the same level.Under the same technological conditions,the larger the sample's specific surface area,the more precipitates in the nitriding layer,the lower the pitting potential,the greater the corrosion current and the worse the corrosion resistance.After the low temperature plasma nitriding treatment of 300 series austenitic stainless steel for 12h by the same process,the surface layer of the samples of 300 series austenitic stainless steel was obtained double nitriding layer.AISI 304 l the permeability after nitriding layer thickness,high surface hardness,and the corresponding minimum friction coefficient,friction coefficient about 0.75,the AISI 316L nitriding carbonitriding layer and surface hardness than AISI 304L is low,its permeability layer corresponds to the friction coefficient of the AISI 304L carbonitriding layer of the friction coefficient is larger,the friction coefficient at around 0.82,AISI 321 nitriding layer of the thinnest,minimum surface hardness,the corresponding maximum friction coefficient,the coefficient of friction at around 0.96;Austenitic stainless steel 300 series low temperature after nitriding,the pitting potential and 300 series austenitic stainless steel substrate to maintain at the same level,the pitting potential at around-0.4115V,AISI304L nitriding samples after corrosion current of 8.522�10^-7 A/cm²,compared the corrosion current AISI304L matrix reduced the one order of magnitude,AISI316L nitriding samples after corrosion current of 3.165�10^-6 A/cm²,AISI321 nitriding samples after corrosion current of 3.441�10^-6 A/cm²,It is not much different from the substrate.