Cr3C2对激光熔覆钴基合金涂层组织与性能的影响

采用5kW CO2连续激光在低碳钢表面激光熔覆了钴基合金涂层(Co60)及添加25％Cr3C2(质量分数)的钴基合金复合涂层(Cr3C2／Co)，对比研究了Cr3C2对熔覆涂层的组织、显微硬度及耐腐蚀磨损性能的影响。结果表明，在本试验条件下可得到熔覆质量良好的Co60及Cr3C2／Co涂层。Co60涂层组织主要由大量初生枝晶γ固溶体及其间的共晶组织γ与(Cr，Fe)7C3组成。Cr3C2／Co涂层组织主要由未熔Cr3C2，大量杆状和块状的富Cr碳化物及其间的非常细小的枝晶及其共晶体组成，主要组成相为γ-Co，Cr7C3，Cr23C6和未熔Cr3C2颗粒。添加的Cr3C2改变了Co60涂层的凝固特征，使Co60涂层的亚共晶结晶方式转变为Cr3C2／Co涂层的过共晶结晶方式。未熔Cr3C2粒子起到了非自发形核作用，在其周围形成了许多富Cr碳化物，并细化了涂层枝晶组织。Cr3C2/Co涂层的显微硬度以及在不同腐蚀介质中的耐磨性比Co60涂层都有明显提高。

Effect of Cr3C2 Particles on Microstructure and Corrosion-Wear Resistance of Laser Cladding Co-based Alloy Coating

Laser cladding Co-based alloy coating (Co60) and Co-based alloy composite coating with 25(mass)% Cr3C2 particles (Cr3C2/Co) on low carbon steel substrate were obtained by 5-kW CO2 continuous wave laser. Effects of Cr3C2 particles on microstructure, micro hardness and corrosion-wear resistance of Co-based alloy coating were discussed. The results showed that the good laser cladding coatings were obtained in the test conditions. The Co60 coating is consisted of many γ-Co dendritic solid solution and eutectic structure (γ-Co and (Cr,Fe)7C3) between the dendrites. The Cr3C2/Co coating is consisted of undissolved Cr3C2 particles, many different shape rich-chromium carbides (M7C3,M23C6) and very finer dendrite and eutectic structure between the carbides. Addition of Cr3C2 particles alters the solidification characteristic of the laser cladding coating Co60, transforming the hypo-eutectic crystal mode of Co60 to hyper-eutectic crystal mode of Cr3C2/Co. Cr3C2 particles play a role of non-spontaneity nucleation, and many rich-chromium carbides are formed around Cr3C2 particles, fining the dendrite structure. Micro-hardness and corrosion-wear resistance in different corrosion media of the Cr3C2/Co coatings are obviously higher than those of Co60 coatings.