Effects Of Surface Complex Treatment Processing On Mechanical Properties And Corrosion Resistance Of Alloy Steel Fastener

The corrosion resistance and fatigue performance of20Cr fastener and42CrMo fastener have been greatly improved after being treated by low temperature gas multicomponent thermochemical treatment and complex treatment processing.The results show that the tensile strength of the SUS304bolt and SUS201bolt are respectively613MPa and748MPa,yield strength are respectively310MPa and385MPa.The surface of the carbonitriding layer is mainly composed of iron compounds,Fe3O4and Fe2O3.Tensile strength are increased significantly up to524MPa and the corresponding yield strength is425MPa; It can be seen that while the tensile strength of20Cr is increased,the yield strength is also increased significantly at the same time. Fatigue test shows that the fatigue performance of20Cr is enhanced significantly after multi-elements penetration compared with raw material and stainless steel.The fatigue strength of SUS304and SUS201are respectively158MPa and169MPa,fatigue strength of process2is between200MPa and238MPa while process3&4are between238MPa and277MPa.Solt spray corrosion test shows that the corrosion resistance of20Cr improves significantly after multi-elements penetration.SUS304starts to rust after120h while SUS201starts to rust after12h,time beginning to rust for multi-elements penetration process20Cr is respectively12h,44h,90h and120h.lt can be seen that the corrosion resistance of process4is consistent with SUS304and the corrosion rate of process4is faster than SUS304after120h.Time beginning to rust for multi-elements penetration process&chemical composite plating processing for20Cr and42CrMo high strength bolt is respectively190h and166h while the grade9is remained for170h which is better than SUS304and SUS201.The corrosion resistance of42CrMo is also better than SUS304and SUS201after multi-elements penetration process&chemical composite plating processing.In conclusion,this experiment explores a kind of new multi-elements penetration process of making fastener with high fatigue performance and corrosion resistance,the technology can be uced to replace the SUS304fastener and SUS201fastener.