Effect Of Plasma Discharge Treatment On The Tribological Properties Of AerMet100 Steel

AerMet100 steel has high strength and toughness matching,excellent fatigue strength and stress corrosion fracture resistance and other comprehensive properties,and its application prospects in the aviation industry are extremely broad.When used as a harmonic reducer bearing under severe impact and long-term wear conditions,the original surface hardness and wear resistance of AerMet100 steel are far from meeting its performance requirements,and serious oxidation,adhesion,friction and wear will occur.Its failure greatly shortens the service life and reduces production efficiency.The use of ion chemical heat treatment to strengthen the surface of AerMet100 steel can effectively improve the phase composition,hardness and wear resistance.In this paper,ion nitriding,ion nitrocarburizing and ion nitrogen-sulfur composite processes were used to modify the surface of AerMet100 steel to enhance the surface hardness and tribological properties of the steel.The main research contents and conclusions of this paper are as follows:(1)Under the condition of 100 Pa constant pressure in the furnace,ion nitriding was used to modify the surface of AerMet100 steel.The tribological properties of the nitriding sample under the conditions of temperature,N₂/H₂and holding time were systematically studied.First,in an atmosphere with N₂/H₂of 1/2,heat preservation treatments at 450°C,480°C and 510°C were carried out for 6 h.It was found that with the increase of temperature,both the compound layer and the permeable layer thickened,and the hardness gradient tended to be gentle.Nitrided samples at 480°C had the lowest wear rate and good wear resistance.Secondly,heat preservation at 480°C for 6 h,nitriding under the conditions of 1/2,1/1 and 2/1 N₂/H₂,respectively.The results show that with the increase of N₂/H₂in the atmosphere,the thickness of the infiltrated layer first increases and then decreases,and the hardness gradient gradually becomes gentle.The sample has good wear resistance when N₂/H₂is 1/1.Finally,at 480°C,N₂/H₂is 1/1,nitriding treatment under the conditions of 2 h,4 h,6 h and 8 h.The results showed that the sample with 4 h heat preservation has the highest surface hardness of 1234.78 HV0.1;when the heat preservation exceeds 6 h,the infiltration layer no longer thickens,and the wear rate decreases with the increase of the heat preservation time.Compared with untreated samples,the wear rate(0.72×10^-5mm³·N^-1·m^-1)of the samples after holding for 8 hours is reduced by nearly 95%,which has the best tribological performance.(2)In order to further improve the problem of large hardness gradient of the nitrided layer,the effect of ion carbonitriding of temperature and methane addition on the frictional properties of AerMet100 steel was systematically studied.First,add 4%of the total gas amount of methane in a 1/1 atmosphere of N₂/H₂to carry out co-permeation treatment with different temperatures and holding for 6 hours.The results show that the compound layer is composed of?,??,Cr N phase and a small amount of Fe₃C phase.The thickness of the infiltrated layer increases with the increase of temperature,and the maximum thickness can reach 157.45?m,while the surface hardness decreases,and the abrasion resistance of the infiltrated sample at 480°C is better.Secondly,the influence of methane content in the atmosphere on the tribological properties of the sample was explored at a constant temperature of 480°C.With the increase of methane addition,the phase of the co-permeable layer does not change,the compound layer thickens,and the hardness of the secondary inner layer decreases faster than the surface layer.When the amount of methane added is 2%,the sample has the lowest friction factor of 0.188 and a wear rate of 0.69×10^-5mm³·N^-1·m^-1,showing the best tribological performance.When the amount of methane added exceeds 3%,cracks will occur in the compound layer and cause collapse.(3)In order to improve the boundary lubrication state of the surface of the hard nitriding layer,the ion sulfide composite treatment is applied.The results show that the composite layer is composed of?,??and Fe S phases,and the thickness can reach 138?m.The formation of a sulfurized layer(2?m)leads to a decrease in surface hardness,but does not affect the hardness of the original nitrided layer.The hard nitriding layer is covered with a soft nitriding layer,which can not only realize the anti-friction and lubrication effect,but also can effectively play the lubrication time of the nitriding layer.After nitrogen-sulfur composite treatment,the sample has the lowest friction factor of 0.21 and wear rate of0.65×10^-5mm³·N^-1·m^-1,and the wear rate is reduced by nearly 96%compared with the untreated sample,which is compared with the nitriding sample Reduced by 1/3,showing the best tribological performance.