Effect of Ion Nitriding on Microstructure and Friction and Wear Property of 38CrMoAl Steel
The surface of 38CrMoAl steel was processed by ion nitriding at 560 ℃ with the mixture of nitrogen and argon as nitrogen source.After that,the friction and wear property of 38CrMoAl steel was studied.The results show that as the N2 volume fraction in the mixed gas increases,the thickness of nitrided layer increases,and the surface hardness of the nitrided layer increases first and then decreases.By adjusting the volume fraction of N2 in the mixed gas,the number of active nitrogen atoms can be changed,thus leading to the change in the phase composition of the nitrided layer.With N2 and Ar in a volume ratio of 2∶3,γ'-Fe4 N phase is the major phase and ε-Fe2-3 N phase is the minor phase in the nitrided sample.With N2 and Ar in a volume ratio of 3∶2,the nitrided layer has ε-Fe2-3 N phase as the major phase and γ'-Fe4 N as the minor phase.Compared with the substrate material,the ion-nitrided sample has a smaller friction coefficient and higher wear-resistance.With N2 and Ar in a volume ratio of 3∶2,the ion-nitrided sample has its compound layer in a thickness of 21.4 μm,and its average friction coefficient up to 0.26,presenting good wear resistance.The mechanisms of friction and wear include fatigue,abrasion and oxidation.
surface treatment38CrMoAl steelion nitridingratio of nitrogen to argoncompound laywear resistanceabrasive wearoxidation wear
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