Research On Wear And Corrosion Resistance Of Catalytic Gas-Nitriding And Post-nitriding Oxidation Treatment

As one of the commonly used surface strengthening methods for metal materials,gas nitriding treatment technology can significantly improve the surface performance.With the rapid development of intelligent manufacturing and precision manufacturing,the wear resistance and corrosion resistance of parts are becoming higher and higher,and traditional gas nitriding urgently needs technological innovation.Through catalytic gas-nitriding and post-nitriding oxidation treatment,the surface performance is further improved,and the service life and precision retention of the parts are extended.Therefore,this subject research has important theoretical research significance and engineering application value in actual production.In this paper,the effect of catalytic gas-nitriding experiments on AISI 304 stainless steel and 12CrlMoV steel was studied to study its effect on the properties of nitriding layer;through the post-nitriding oxidation experiment of DT4C pure iron and FN04Mo powder metallurgy,the post-nitriding oxidation mechanism was studied.Characterized and analyzed the microstructure using optical microscope(OM)and field emission scanning electron microscope(FESEM);Use X-Ray diffractometer(XRD)and electron microprobe(EPMA)to analyze the sample phase,composition and elements;Evaluate the mechanical properties of the sample surface by micro hardness tester and nano indenter;The salt spray test machine,electrochemical workstation,multifunctional friction and wear test machine,and three-dimensional profilometer were used to evaluate the corrosion resistance and wear resistance of the samples.The results show that:(1)Using catalytic gas-nitriding,the depth of the nitriding layer of AISI 304 stainless steel is increased by 12.7 ?m,the surface hardness is increased by about 100.0 HV0.05,the nitrogen concentration of the diffusion layer is increased by nearly 1 times;12Cr1MoV increases the strength while maintaining Good toughness.(2)The active components in the catalyst react with the passivation film in a nitriding atmosphere to form small particles of composite oxide,destroy the original uniform and dense structure,and achieve the effect of breaking the passivation film.(3)After the AISI 304 stainless steel is catalyzed at 530?,the nitrogen concentration of the nitrided layer increases,accelerating the precipitation of chromium-nitrogen compounds and local chromium depletion,resulting in a compound layer with a lower potential than the substrate electrode,and the corrosion resistance is reduced.(4)The oxide layer may be formed in two ways:one is that the nitride in the compound layer is first decomposed into Fe and then reacts with oxygen to form an oxide,and the other is that oxygen in the atmosphere directly reacts with the nitride to form an oxide.Too high post-nitriding oxidation temperature and too long time will aggravate the decomposition of nitride,resulting in delamination and loosening of the oxide film,while increasing the proportion of Fe2O3.(5)After post-nitriding oxidation treatment,the surface of FN04Mo is military black,the surface nano-indentation hardness reaches 7.78 GPa,the core hardness is 419.7 HV0.2,and the salt spray test can reach 264 h without rust.(6)Oxidation after nitriding can improve the corrosion resistance and wear resistance,and the increase in temperature and time will reduce the corrosion resistance and wear resistance.