WC含量对激光熔覆CoCrFeNiTi高熵合金涂层组织及耐腐蚀性能的影响

Effect of WC Content on Microstructure and Corrosion Resistance of Laser Cladding CoCrFeNiTi High-entropy Alloy Coating

摘要:

为了延长脱硫浆液循环泵叶轮的寿命，采用激光熔覆技术在脱硫浆液循环泵叶轮的母材30CrMnSiA钢表面制备了WC增强CoCrFeNiTi-WCx(x=0、5、10、15、20wt%)高熵合金涂层，系统研究了WC含量对涂层的显微组织、力学和耐蚀性能影响。研究发现CoCrFeNiTi高熵合金涂层相组成为FCC(Fe-Ni)、BCC(Fe-Cr)、Laves(CoTi2)和AB-type(Ti的化合物)，随着WC含量增加，Laves相衍射峰强度增强，且生成了新相碳化物（WC、TiC、Cr7C3和Fe3C）。CoCrFeNiTi高熵合金涂层主要组织为底部的胞状晶和顶部的等轴枝晶，随着WC含量增加，涂层组织主要为等轴枝晶，且晶粒尺寸逐渐细化。WC的加入提高了涂层的性能，其中CoCrFeNiTi-20%WC涂层硬度最大（654.955 HV0.2），且摩擦系数（0.664）和磨损率（1.3×102 um3?s -1?N-1）最小，耐磨性能最好，磨损机制主要为轻微的黏着磨损和磨粒磨损。此外，随着WC含量增加，涂层表现出更低的腐蚀速率和腐蚀电流。其中，CoCrFeNiTi-20%WC涂层腐蚀电流最小，耐腐蚀性能最好。

Abstract:

To prolong the life of the desulfurization slurry circulating pump impeller. In this study, WC-reinforced CoCrFeNiTi-WCx(x=0, 5, 10, 15, and 20 wt%) high–entropy alloy (HEA) coatings were fabricated on the base material 30CrMnSiA steel surface of desulfurization slurry circulating pump impeller by laser cladding. The effects of WC content on the microstructure, phase composition, element distribution, microhardness, wear resistance, and corrosion resistance of the coatings were systematically studied. It was found that the phase composition of CoCrFeNiTi HEA coating was FCC (Fe-Ni), BCC (Fe-Cr), Laves (CoTi2), and AB-type (compounds of Ti) phases. With the increase of WC content, the diffraction peak intensity of Laves phase increased, and new phases carbides (WC, TiC, Cr7C3, and Fe3C) were formed. The microstructure of CoCrFeNiTi HEA coating was mainly composed of cellular crystals at the bottom and equiaxed dendrites at the top. With the increase of WC content, the coating microstructure was mainly equiaxed dendrites, and the grain size gradually refined. The addition of WC improved the performance of the coatings, among which the CoCrFeNiTi-20% WC coating had the largest microhardness of 654.955 HV0.2 and the smallest coefficient of friction (0.664) and wear quality(1.3×102 um^3?s^(-1)?N^(-1)), the best wear resistance, and the wear mechanism was mainly slight adhesive wear and abrasive wear. In addition, with the increase of WC content, the coating showed lower corrosion rate and corrosion current. Among them, CoCrFeNiTi-20%WC coating had the smallest corrosion current and the best corrosion resistance.