WC含量对激光熔覆NiCrBSi-WC复合涂层显微结构及力学性能的影响

Effect of WC Particle Content on Microstructure and Mechanical Properties of Laser Cladded NiCrBSi-WC Composite Coating

目的为盾构、勘探及采矿等高载荷严苛磨损条件下的构件表面防护提供一种新的涂层方法。方法以激光熔覆技术为手段,在NiCrBSi粉末中混入30%~80%(体积分数)的球形WC颗粒,用以制备NiCrBSi-WC复合涂层。研究了WC颗粒含量对涂层显微组织形成、硬度、断裂韧性和耐磨性的影响规律。采用SEM分析了涂层的显微组织;通过显微维氏硬度计测试涂层的硬度;通过压痕法测试涂层的断裂韧性;采用磨粒磨损试验表征涂层的耐磨性。结果当WC颗粒体积分数低于60%时,熔融金属的黏度较低,密度更大的WC颗粒会沉淀,导致涂层表层的WC颗粒含量较低;当WC颗粒体积分数介于60%~80%时,WC颗粒在涂层内均匀分布,涂层内无气孔及裂纹等缺陷。当WC颗粒体积分数达到80%时,熔体黏度过大,使气体难以及时逸出,在涂层内形成大量气孔。随着WC体积分数由30%上升到80%时,涂层的平均硬度由67HRC提高到85HRC。涂层的断裂韧性随WC含量的提高,出现先升高后下降的反常现象。60%WC含量的复合涂层表现出最佳的耐磨性,比滚刀常用材料H13钢提高约9倍。结论采用常规激光熔覆技术时,添加40%~60%范围内的硬质陶瓷颗粒,可获得硬质颗粒分布均匀且耐磨性与抗冲击性能优异的复合涂层。

The work aims to provide a new coating method for protecting component surface under severe wear conditions of high load during shielding,exploration,mining,etc.NiCrBSi/WC composite coating was prepared by laser cladding through adding 30%~80% spherical WC particles in NiCrBSi powders.Effect of the WC particle content on microstructure formation, hardness,fracture toughness and abrasive wear resistance was systematically investigated.Microstructure of coating was analyzed by SEM,hardness was tested by the Vickers hardness tester,the fracture toughness was investigated by indentation method and the wear resistance was characterized by abrasive wear test.When mass fraction or volume fraction of WC particle was lower than 60%,the viscosity of molten metal was lower,and WC particles with higher density precipitated,resulting in lower WC particle content in the coating surface layer.When the content of WC particles ranged from 60% to 80%,WC particles were uniformly distributed in the coating,and there were no defects such as pores and cracks in the coating.As mass fraction of WC particles increased to 80%,the melt viscosity was too high,which made it difficult for gas to escape in time and formed a large number of pores in the coating.As the WC mass fraction increased from 30% to 80%,the average hardness of the coating increased from 67HRC to 85HRC.The fracture toughness of the coating increased first and then decreased with the increase of WC content.The composite coating with 60%WC content showed the best wear resistance,which was about 9 times higher than that of H13 steel as the common hob material.When conventional laser cladding technology is adopted,a composite coating with uniform distribution of hard particles and excellent wear resistance and impact resistance can be obtained by adding hard ceramic particles in the range of 40%~60%.