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    WC含量对激光熔覆WC/15-5PH不锈钢复合涂层组织和性能的影响

    Influence of WC Content on Microstructure and Properties of WC/15-5PH Steel Composite Coating by Laser Cladding

    • 摘要: 采用激光熔覆在Q235钢表面制备WC质量分数分别为0,10%,20%,30%的15-5PH不锈钢涂层,研究了涂层的微观结构、显微硬度、耐磨性能和耐腐蚀性能。结果表明:不含WC的15-5PH不锈钢涂层主要由α-Fe、马氏体和Fe-Cr等组成,含质量分数10% WC的WC/15-5PH不锈钢复合涂层主要由α-Fe、马氏体、Fe-Cr、(Fe, Ni)、Cr7C3、Cr23C6和WC等组成,随着WC含量继续增加,涂层中出现新相W2C。随着WC含量增加,涂层中柱状晶数量减少,等轴晶数量增加,晶粒明显细化,涂层中未分解的WC以及新生成的W2C、Cr7C3和Cr23C6等碳化物颗粒数量增加。随着WC含量增加,涂层的显微硬度升高,摩擦因数和磨损率均降低;含质量分数30% WC的涂层硬度最高,为539 HV,相较于15-5PH不锈钢涂层提高约41%,摩擦因数和磨损率最低,分别为0.423 6和1.01×10−5 mm3·N−1·m−1,相较于15-5PH不锈钢涂层分别降低约18%和73%,涂层的主要磨损机制为氧化磨损、黏着磨损并伴有极少量磨粒磨损。相较于基体,涂层的自腐蚀电位更正,自腐蚀电流密度更小,容抗弧半径更大,耐腐蚀性能优于基体;随着WC含量增加,涂层的自腐蚀电流增大,容抗弧半径减小,耐腐蚀性能降低。不含WC的15-5PH不锈钢涂层的自腐蚀电流最小,为2.64×10−6 A·cm−2,自腐蚀电位较正,为−0.451 V,容抗弧半径最大,耐腐蚀性能最佳。

       

      Abstract: 15-5PH stainless steel coatings with WC mass fractions of 0, 10%, 20%, and 30% were prepared on the surface of Q235 steel by laser cladding. The microstructure, microhardness, wear resistance, and corrosion resistance of the coatings were studied. The results show that the 15-5PH stainless steel coating without WC was mainly composed of α-Fe, martensite, and Fe-Cr; the WC/15-5PH stainless steel composite coating with WC mass fraction of 10% was mainly composed of α-Fe, martensite, Fe-Cr, (Fe, Ni), Cr7C3, Cr23C6, and WC. As the WC content further increased, a new phase W2C appeared in the coating. With the increase of WC content, the number of columnar crystals in the coating decreased, the number of equiaxed crystals increased, the grains became significantly finer, and the number of undecomposed WC and newly generated W2C, Cr7C3, and Cr23C6 carbide particles in the coating increased. With the increase of WC content, the microhardness of the coating increased, and the friction coefficient and wear rate decreased. The coating with WC mass fraction of 30% had the highest hardness of 539 HV, which was approximately 41% higher than that of the 15-5PH stainless steel coating; the friction coefficient and wear rate were the lowest, being 0.423 6 and 1.01×10−5 mm3·N−1·m−1, respectively, which were approximately 18% and 73% lower than those of the 15-5PH stainless steel coating. The main wear mechanism of the coating with WC mass fraction of 30% was oxidation wear, adhesion wear, and a small amount of abrasive wear. Compared to the substrate, the self-corrosion potential of the coating was more positive, the self-corrosion current density was smaller, the capacitive arc radius was larger, and the corrosion resistance was better than that of the substrate. With the increase of WC content, the self-corrosion current of the coating increased, the capacitive arc radius decreased, and the corrosion resistance decreased. The self-corrosion current of the 15-5PH stainless steel coating without WC was the smallest, being 2.64×10−6 A·cm−2, with a relatively positive self-corrosion potential of −0.451 V, and the largest capacitive arc radius, achieving the best corrosion resistance.

       

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