QPQ处理工艺对F690钢渗层微观结构及磨蚀性能的影响

利用QPQ技术对F690海工钢进行盐浴复合强化处理,考察了碳氮共渗温度和时间对F690钢渗层组织、相结构及硬度、腐蚀磨损性能的影响。结果表明:经过QPQ处理后,F690钢表面形成由Fe₃O₄氧化层、Fe₂C/Fe₂N化合物层及扩散层组成的渗层,且渗层组织平整均匀。随着QPQ处理温度升高和时间延长,渗层厚度增加,渗层硬度均呈先增大而后减小的变化规律;当共渗温度为570 ℃、时间为60 min时,F690钢的渗层硬度达854HV,较F690钢硬度提高1.7倍。与F690钢相比,3.5%NaCl介质下渗层的自腐蚀电流密度降低了一个数量级,腐蚀速率降低了86.71%,摩擦系数下降约12%,磨损率显著降低。

Influence of QPQ Process on Microstructure and Corrosion Wear Properties of F690 Steel Nitriding Layer

F690 steel for marine engineering was processed by Quench-Polish-Quench complex salt bath process (QPQ). The influences of nitriding temperature and time on the microstructure, phase structure, hardness, corrosion and wear properties of F690 steel were investigated. The results showed that after QPQ treatment, a nitriding layer, composed of Fe₃O₄ oxide layer, Fe₂C, Fe₂N compound layer and diffusion layer, was formed on the surface of F690 steel with smooth and uniform microstructure. With the increasing of the nitriding temperature and the prolonging of nitriding time of salt bath, the thickness of the nitriding layer increased and the hardness of nitriding layer decreased after an initial increase. The hardness of nitriding layer maximally reached 854HV with the nitriding temperature at 570 ℃ and the nitriding time of 60 min, indicating 1.7 times higher than that of F690 steel. Compared with F690 steel, the current density for self-corrosion of the infiltration layer with 3.5%NaCl medium was decreased by an order of magnitude, the corrosion rate was decreased by 86.71%, the friction coefficient was declined by 12%, and the wear rate was also decreased remarkably.