【摘要】 在低碳钢表面激光熔覆制备了添加质量分数40%Cr3C2的钴基合金复合涂层(Cr3C2/Co),研究了激光熔覆Cr3C2/Co涂层的显微组织、相结构、显微硬度及其摩擦磨损性能,并与激光熔覆钴基合金涂层(Co60)进行了相同工艺条件下的对比试验.结果表明,激光熔覆Co60涂层以亚共晶方式结晶,涂层组织主要由大量初生γ-Co枝晶固溶体及其间的共晶组织γ-Co+Cr23C6组成;激光熔覆Cr3C2/Co涂层以过共晶方式结晶,组织主要由未熔Cr3C2粒子、大量杆状和块状的富Cr碳化物(M7C3及M23C6型碳化物)以及其间的细小枝晶与共晶组织组成.添加Cr3C2改变了Co60涂层的凝固特征,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,细化了涂层枝晶组织.激光熔覆Cr3C2/Co涂层的显微硬度及其耐磨性比Co60涂层明显提高.Co60涂层主要磨损机理为脆性剥落和犁削,Cr3C2/Co涂层的磨损机理主要为轻微犁削.更多还原

【Abstract】 Laser cladding Cobalt-based alloy coating（Co60） and Cobalt-based composite coating doped with 40% Cr₃C₂ particles（Cr₃C₂/Co） were prepared on the low carbon steel substrate by 5 kW CO₂ laser.Microstructures of the coatings were analyzed by optical microscopy and scanning electron microscopy,and the phase composition and elemental composition of the coatings were determined by X-ray diffraction and energy dispersive X-ray analysis. Moreover,microhardness of the coatings were measured,and friction and wear behaviors of the coatings sliding against H13 alloy with laser cladding WC/Ni coating in a block-on-ring configuration were evaluated on an MM-200 test rig.Worn surface morphologies of the coatings were also observed by scanning electron microscopy.It was found that the Co60 coating was crystallized in hypo-eutectic crystal mode,and consisted of many γ-Co dendritic solid solution and eutectic structure(γ-Co and Cr₂₃C₆) between the dendrites.Cr₃C₂/Co coating was crystallized in hyper-eutectic crystal mode and consisted of undissolved Cr₃C₂ particles,rich-chromium carbides(M₇C₃ and M₂₃C₆) with different shapes and fine dendrite and eutectic structure between the carbides.Addition of Cr₃C₂ particles altered the solidification characteristic of the Co60 coating.Undissolved Cr₃C₂ particles played a role in non-spontaneous nucleation,and rich-chromium carbides were formed around Cr₃C₂ particles,and dendrite microstructure was refined.Cr₃C₂/Co coatings has higher micro-hardness and it exhibited better wear resistance than that of the Co60 coatings.Wear of the Co60 coating was dominated by brittle spalling and ploughing,while the Cr₃C₂/Co coatings was dominated by ploughing.更多还原