表层绝热对定向凝固Ni60合金涂层凝固行为的影响

Effects of Surface Insulation on Solidification Behavior of Directional Solidified Ni60 Alloy Coating

采用超音速等离子喷涂技术在45钢基体上制备Ni60合金涂层,在高频感应重熔+强制冷却处理条件下,研究了表面散热条件对涂层的组织结构、元素分布和性能的影响。结果表明:在自然散热条件,涂层形成了定向树枝晶结构组织,通过表面覆盖层的保护,改变表面散热条件,使涂层组织向具有熔结特征的等轴晶转变,并且形成了两个明显不同组织的区域,在靠近基体区域,组织细小致密,但组织和元素分布不均匀;而靠近涂层表面区域,组织具有长大现象,但元素和组织均匀性明显提高。相对于未加覆盖层涂层,附加覆盖层的涂层元素和基体元素在界面处具有更充分的扩散,基体元素向涂层中的扩散较涂层元素向基体扩散更加强烈。覆盖层的附加明显提高了涂层硬度,使涂层表面的宏观硬度由33.4 HRC提高到54.4 HRC,涂层截面的显微硬度由566.1 HV0.2提高到659.2 HV0.2。

The Ni60 alloy coating was prepared by supersonic plasma spraying on 45 steel substrate, and the effect of ceramic coverage on the microstructure, element distribution and properties of the coatings was investigated under high-frequency induction remelting and forced cooling treatment. The results show that compared with the structure of directional dendrites without covering, the coating structure of coverage protection is changed to equiaxed grain with melting characteristic, and forms two distinct areas of microstructure. Nearing the substrate area, the microstructure is fine compact while the microstructure and elements are not evenly distributed. Nearing the coating surface area, the microstructure grows up, while the uniformity of elements and microstructure increases obviously. Compared with the coating without covering, the elements between the coating and the substrate diffuse more fully at the interface with additional coverage, and the diffusion of substrate elements to coatings is more intense. The addition of the coverage significantly improves the hardness of the coating, and the macrohardness of the surface of the coating increases from 33.4 HRC to 54.4 HRC, the microhardness of the cross section of the coating increases from 566.1 HV0.2 to 659.2 HV0.2.