渗氮对激光熔覆(NiCr)_(92-x)Mo_(8)Ti_(x)涂层组织与耐磨耐蚀性能的影响

Effect of nitriding on microstructure and wear and corrosion resistance of laser cladding(NiCr)_(92-x)Mo8Ti x coatings

首先采用激光熔覆技术在304不锈钢(304SS)表面制备了(NiCr)_(92-x)Mo_(8)Ti_(x)涂层,随后对其进行了渗氮处理。采用X射线衍射仪、扫描电镜、显微硬度计、摩擦磨损实验及电化学工作站等对渗氮前后涂层的物相组成、显微组织、硬度、耐磨性和耐蚀性进行了分析。结果表明:激光熔覆(NiCr)_(92-x)Mo_(8)Ti_(x)涂层主要由FCC相、σ-CrMo相和少量的Cr_(2)Ti相组成,经渗氮处理后涂层中有(Cr, Ti)N相生成;随着Ti含量增加,(Cr, Ti)N相的含量和渗氮层厚度增加;渗氮后涂层的硬度显著增加(最高达到1258 HV0.1),摩擦系数降低,磨损量显著减少,耐磨性得到显著提高,磨损机制从粘着磨损转变为磨粒磨损。在3.5 mass%NaCl溶液中,经过渗氮处理后涂层的腐蚀电流密度显著降低,且没有点蚀现象发生,浸泡腐蚀实验也表明经过渗氮后的涂层表面腐蚀程度远小于未进行渗氮的涂层,表明渗氮后涂层的耐蚀性显著提高。

Firstly,(NiCr)_(92-x)Mo8Ti x coatings were prepared on the surface of 304 stainless steel(304SS)using laser cladding technology,followed by nitriding treatment.Phase composition,microstructure,hardness,wear resistance and corrosion resistance of the coatings before and after nitriding were analyzed by means of X-ray diffraction,scanning electron microscopy,microhardness tester,friction and wear experiment,and electrochemical workstation.The results show that the laser cladding(NiCr)_(92-x)Mo8Ti x coatings are mainly composed of FCC phase,σ-CrMo phase and a small amount of Cr_(2)Ti phase,and(Cr,Ti)N phase is observed in the coatings after nitriding.As the Ti content increases,the content of(Cr,Ti)N phase and the thickness of the nitrided layer increase.After nitriding,the hardness of the coatings significantly increases(up to 1258 HV0.1),the friction coefficient decreases,the wear amount significantly decreases,the wear resistance is significantly improved,and the wear mechanism changes from adhesive wear to abrasive wear.In a 3.5 mass%NaCl solution,the corrosion current density of the coatings after nitriding significantly decreases,and there is no pitting phenomenon.The immersion corrosion experiment also shows that the surface corrosion degree of the coatings after nitriding is much lower than that of the coatings without nitriding,indicating a significant improvement in the corrosion resistance of the coatings after nitriding.