激光熔覆复合涂层组织性能研究

Microstructure and Properties of Laser Cladding WC-12Co / NiCrAIY Coating

研究了TC4合金表面激光熔覆WC-12Co/NiCrAlY复合涂层后熔覆层的组织结构、显微硬度、熔覆层深度等。实验结果表明,激光熔覆层在组织结构上分为熔化区、结合区、热影响区。由于涂层中不同部位成分、温度分布及冷却速度不同使初生相呈树枝状、块状、花瓣状及颗粒状等几种形态;实现了涂层与基体的良好冶金结合,熔覆层最高硬度可达1100 HV。利用SEM观察、显微硬度测试等分析手段,研究了激光功率、扫描速度、涂层成分、涂层厚度对熔覆层的显微硬度、熔覆层深度影响。结果表明:在其它条件不变时,随着能量密度的增加,熔覆层的显微硬度下降;随着涂层成分中WC-12Co相对含量的增加,熔覆层的硬度增加,但熔覆层的深度减小;激光能量密度大小对熔覆层中熔化区的深度有较大影响;随着涂层厚度的增加,熔化区的深度在减小。

In this paper,the structure、microhardness and the distribution characteristics of composition of laser clad zone of WC- 12Co and NiCrAlY on TC4 were studied.Cross-section of the laser clad zone showed three distinct regions which consisted of melt zone,bonding zone and heat-affecting zone.The result showed that laser cladding leads to the formation of a continue and compact clad layer.The difference in the composition,temperature and cooling speed in different areas of the coating leads to the result that there are several kinds of structural feathers including dendritic,polgon lumpish,petaloitic,petal and particulate.The metallurgical combining interface between the cladding layer and matrix is achieved.The maximum of the microhardness of WC -12Co and NiCrAlY layers cladded by laser comes up to 1 100 HV. The influence of laser power and coating thickness on the microhardness of the clad zone,on the thickness of clad-layer and the depth of melt zone were studied using scanning electron microscope（SEM） and microhardness testing techniques.The result showed that given the WC-12Co and NiCrAlY coating thickness constant,the depth of clad-layer increases while the microhardness of clad zone decreases with the increment of laser power.