直流等离子氮化工艺对316L不锈钢组织和磨损的影响

INFLUENCE OF PROCESS PARAMETERS ON MICROSTRUCTURE AND WEAR PROPERTY OF 316L STAINLESS STEEL BY HIGH VOL TAGE DC PLASMA GLOW-DISCHARGE NITRIDING

应用高压直流辉光放电等离子技术，改变氮化工艺参数，对316L奥氏体不锈钢进行表面渗氮处理。利用XRD衍射仪分析渗氮层的相组成，SEM观察氮化层厚度和结构，表面显微硬度计检测渗层的表面硬度，结果表明：当氮化温度T为400℃时，氮化层为单一的S-phase；当420℃≤T〈480℃时，氮化层为CrN＋S—phase两相混合；当温度为480℃时，S—phase衍射峰消失，仅出现CrN相；渗层厚度约为5～9μm，渗层深度随着温度和气压的升高而增加；表面显微硬度随着温度和气压的增加而增加，最高的表面显微硬度可达839Hv0.1。在MM200磨损实验机上用环块式的方法评价磨损性能，结果表明等离子氮化显著提高了不锈钢表面的耐磨性能；用SEM观察磨损表面形貌，表明未氮化的不锈钢的磨损机制主要是粘着磨损、氧化磨损和磨粒磨损；等离子氮化试样的磨损机制主要是氧化磨损。

316L stainless steel was surface modified by high voltage DC plasma glow discharge nitriding （DCPN） with different process parameters. The phase composition of the plasma nitrided layer was examined by means of X ray diffraction, the thickness and structure was investigated by SEM and the surface hardness by micro hardometer. It showed that a homogenous layer of expanded austenite was produced at 400℃, a nitri ded layer of mixture（CrN＋S-phase） at 420℃≤T〈480℃, and a single layer of CrN at 480℃. The thickness of nitrided layer was approximately 5-9μm, which increased with the temperature and pressure increasing. The maximum hardness of nitrided samples at surface could reach 839Hv0.1. The wear behaviors of DCPN- treated and untreated 316L stainless steel were evaluated on an MM-200 friction and wear tester in a ring-on-block contact configuration. It showed that the wear resistance of stainless steel could be significantly improved by DCPN. The morphologies of the worn surfaces were observed using a scanning electron microscope （SEM）. The wear of the untreated 316 stainless steel was severe and characterized by strong adhesion, abrasion and oxidation wear, while the wear mechanism of the DCPN-treated 316 stainless steel was dominated by oxidation wear.