激光熔覆Co+Ni/WC复合涂层的组织和磨损性能

Microstructure and wear resistance of laser cladding Co+Ni/WC alloy composite coating

关键词:  激光熔覆  钴基合金  组织  磨损性能

Key words:  laser cladding  Co-based alloy  microstructure  wear resistance

摘要:

在低碳钢表面激光熔覆了钴基合金涂层(Co60)以及添加不同含量镍包WC(10%,20%,质量分数)的Co+Ni/WC复合涂层,比较研究了几种涂层的组织与磨损性能。结果表明,Co60涂层主要由初生γ-Co枝晶及其间的共晶组织γ+Cr₂₃C₆组成;Co+Ni/WC涂层主要由未熔WC,γ-Co枝晶及细小的共晶组织组成,主要组成相有γ-Co,Cr₇C₃,Co₃W₃C和未熔WC等。添加WC改变了Co60涂层的定向枝晶生长模式,并细化了枝晶组织。且WC加入量提高,效果越明显。激光熔覆过程中WC颗粒与钴基合金界面间发生了扩散反应溶解,镍包覆有助于WC的残存。与Co60涂层相比,Co+Ni/WC复合涂层的硬度与耐磨性均明显提高,Co+20%WC涂层的抗磨损性能提高1倍以上。

Abstract:

Laser cladding Co-based composite coating(Co+Ni/WC) have been obtained on low carbon steel substrate. Microstructure and wear resistance of the composite coatings were investigated compared with the Co-based coating(Co60). It is indicated that the Co60 coating was composed of primary dendrite of γ-Co and the eutectics of γ-Co+Cr₂₃C₆ among the interdendritics, and Co+Ni/WC composite coatings were composed of γ-Co dendrite and the small eutectics, which consists of γ-Co, Cr₇C₃, Co₃W₃C and unmelted WC particles. With more WC particles, there was further influence to Co60 coating that the directional solidification of dendrite was changed and the dendrite was finer. Owing to the Ni alloy wrapper, the WC particles had been protected from melt for the diffusion reaction on interface between the WC particles and the Co based alloy. Compared with Co60 coating, the hardness and wear resistance of the Co+Ni/WC composite coatings had been improved and the wear resistance of the Co+20% WC composite coating was twice of that of the Co60 coating.