离子渗氮对38CrMoAl钢组织及摩擦磨损性能影响

Effect of Ion Nitriding on Microstructure and Friction and Wear Property of 38CrMoAl Steel

560℃下,以氮气和氩气的混合气体为氮源,对38CrMoAl钢表面进行离子渗氮,研究了离子渗氮后38CrMoAl钢的磨擦磨损性能。结果表明,随着混合气体中N2体积分数增大,渗氮层厚度增加,渗氮层表面硬度呈现先增大后减小的趋势。通过调节混合气体中N_(2)的体积分数,可以改变活性氮原子数量从而改变渗氮层的物相组成,当N_(2)和Ar体积比2∶3时,渗氮层中以γ′-Fe4N相为主相、ε-Fe_(2-3)N相为次相;当N2和Ar体积比3∶2时,渗氮层中ε-Fe_(2-3)N相成为主相、γ′-Fe_(4)N相为次相。与基体材料相比,离子渗氮试样具有更小的摩擦系数,耐磨性得到提高,在N2和Ar体积比3∶2时,渗氮试样的化合物层厚度为21.4μm,平均摩擦系数达到0.26,表现出良好的耐磨性。摩擦磨损机制为疲劳磨损、磨粒磨损和氧化磨损。

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 N_(2) and Ar in a volume ratio of 2∶3,γ′-Fe4N phase is the major phase andε-Fe_(2-3) N phase is the minor phase in the nitrided sample.With N_(2) and Ar in a volume ratio of 3∶2,the nitrided layer hasε-Fe_(2-3)N phase as the major phase andγ′-Fe_(4)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 21.4μm,and its average friction coefficient up to 0.26,presenting good wear resistance.The mechanisms of friction and wear include fatigue,abrasion and oxidation.