纳米WC对AlCoCrFeNi高熵合金涂层耐磨与耐蚀性能的影响

Effect of Nano WC on Wear and Corrosion Resistances of AlCoCrFeNi High-entropy Alloy Coating

AlCoCrFeNi高熵合金具有良好的力学性能、耐磨性能以及抗蚀性能,可作为易损零部件的涂层材料。为进一步提高AlCoCrFeNi涂层性能,本工作通过机械混粉的方式对AlCoCrFeNi和AlCoCrFeNi+WC(5%)(添加5%质量分数的碳化钨)高熵合金粉末进行预处理,在45#钢表面通过激光熔覆制备了涂层,并对比研究了两种涂层的表面形貌、微观组织、元素分布、显微硬度、摩擦磨损及耐蚀性能。结果表明,AlCoCrFeNi+WC(5%)涂层表面粗糙度更低,涂层仍为体心立方结构(BCC/B2),且其晶粒组织得到了细化,W元素和Cr元素富集在晶界处,因细晶强化和第二相强化效应共同作用,涂层平均显微硬度从500HV提高到了600HV。选用直径为4 mm的Si_(3)N_(4)小球作为摩擦副,在10 N的载荷下测试30 min。与AlCoCrFeNi涂层相比,WC的掺杂使摩擦系数从0.8减小到0.6,磨损失重减少了0.84 mg,磨损划痕宽度和深度较小,磨损程度较轻。在3.5%(质量分数)NaCl溶液的电化学测试中,经过WC掺杂的涂层的自腐蚀电位提高了0.042 V,自腐蚀电流密度降低了一个数量级,同时该涂层表现出较大的电容弧直径,且测试后表面腐蚀坑明显减少,腐蚀程度较轻。这表明纳米WC的添加有效提高了AlCoCrFeNi高熵合金涂层的耐磨与耐蚀性能。

AlCoCrFeNi high-entropy alloys have good mechanical properties,wear resistance,and corrosion resistance,which can be used as a coating material for vulnerable parts.AlCoCrFeNi and AlCoCrFeNi+WC(5wt%)high-entropy alloy powders were pretreated by mechanical powder mixing,and afterwards the coatings were prepared by laser melting on the surface of 45#steel,in order to further improve its performance.The surface morphology,microstructure,element distribution,microhardness,friction wear,and corrosion resistance of the two coatings were comparatively studied.The results show that the surface roughness of the AlCoCrFeNi+WC(5%)coating is lower,that the coating still has a body-centered cubic structure(BCC/B2)and that the grain structure of the coating has been refined,with W and Cr elements concentrated at the grain boundaries.The average microhardness of the coating was increased from 500HV to 600HV due to the combined effect of fine grain strengthening and second phase strengthening.The Si_(3)N_(4) sphere with 4 mm diameter was selected as the friction substrate and tested under a load of 10 N for 30 min.The doping of WC reduced the friction coefficient from 0.8 to 0.6,the wear weight loss was reduced by 0.84 mg,the width and depth of wear scratches were minimized,and the wear level was lighter,compared with those of the AlCoCrFeNi coating.In the electrochemical test with a 3.5wt%NaCl solution,the self-corrosion potential of the WC-doped coating increased by 0.042 V,while the self-corrosion current density reduced by one order of magnitude,and the WC-doped coating exhibited a larger capacitive arc diameter.After the test,the AlCoCrFeNi+WC(5%)coating showed lighter corrosion,and the corrosion pits on its surface were significantly reduced.These results indicate that the addition of nano WC can effectively improve the wear and corrosion resistances of the AlCoCrFeNi high-entropy alloy coating.