QPQ氮化时间对316L不锈钢组织和性能的影响

Effects of QPQ Nitriding Time on Microstructure and Properties of 316L Stainless Steel

对316L不锈钢进行了QPQ(Quench-Polish-Quench)处理,研究了600℃渗氮温度下保温(60、90、120、150和180min)后渗层的组织和性能。利用光学显微镜、SEM、XRD、显微维氏硬度计和摩擦磨损机分析材料渗层的显微组织、物相、硬度和耐磨性。结果表明,316L不锈钢经QPQ处理后,渗层表面氧化层由Fe3O4组成,中间化合物层的物相主要包括Fe2~3N、Fe4N、Cr N和α-N相,靠近基体的扩散层主要由Cr N和γN相组成。随着渗氮时间延长,化合物层厚度从60 min的16.54μm增加到180 min的34.94μm,化合物层厚度与渗氮时间呈抛物线关系。与未处理试样相比,QPQ处理试样硬度值提高了4~6倍。干摩擦磨损测试表明,未处理试样表面发生粘着磨损,磨损量和磨损率较大;渗氮后150 min试样耐磨性最好。

QPQ（Quench-Polish-Quench） treatment was carried out on 316L stainless steel by nitriding at 600℃ for varied time（60, 90, 120, 150 and 180 min）. The microstructure, phase constituent, hardness and wear resistance of modified surface layer of the 316L stainless steel were investigated by means of optical microscopy, SEM, XRD, micro-hardness testing and Wear resistance testing. The results reveal that after QPQ treatment for 316L stainless steel, Fe304 oxidized layer is formed on the top of the compound layer, and middle compound layer consists of Fe2-3N,Fe4N,CrN and a-N, while the diffusion layer is composed of CrN and YN. The thickness of the compound layers is increased from 16. 54μm to 34.94μm with the increase of nitriding time from 60 min to 180 min, and the thickness of the compound layer exhibits parabolic relation with the nitriding time. The micro-hardness of QPQ treated samples is increased by 4-6 times higher than that of the untreated sample, and the maximum microhardness value of 1 040.1 HV02 can be obtained after nitriding for 150 min. With prolonging nitriding time, the surface hardness is decreased due to the porosity in the surface layer. The wear resistance of 316L stainless steel can be improved significantly by QPQ treatment, and the optimum nitriding duration for improving the wear resistance is 150 min. The worn surface morphology reveals that the un-treated samples are characterized by adhesive wear, so wear rate is the higher.