【摘要】 针对铸铁激光熔覆涂层结合界面淬火硬化、裂纹倾向大的问题,提出激光合金化与激光熔覆相结合的工艺在蠕墨铸铁表面制备NiCoCrAlY合金涂层。通过光学显微镜、扫描电子显微镜、X射线衍射仪、维氏硬度计研究了激光合金化熔覆中熔覆层稀释率、组织、显微硬度的演化规律,通过三点弯曲试验考察了熔覆层的结合特性及力学性能。结果表明:激光合金化熔覆工艺方法将热影响区由马氏体组织转变为回火索氏体组织,降低了淬硬层深度,改善了熔覆层结合特性与塑性,抗弯强度提高到891MPa。断口显示,熔覆层与基体结合良好,断裂机制是脆性解理断裂与韧窝断裂混合机制。更多还原

【Abstract】 Considering the problem of quench hardening and cracking at the interface of laser cladding coating on the cast iron,a method combined laser alloy and laser cladding was proposed to produce NiCoCrAlY coating on compacted graphite iron. The dilution,microstructure and microhardness of the coating were investigated by means of optical microscope,scanning electron microscopy,X-ray diffractometer,Vickers hardness tester. The bonding characteristics and mechanical properties of the layer were evaluated by three-point bending test. The results show that martensite turns to tempered sorbite in heat affected zone by the laser alloy cladding method,thus the depth of hardening layer decreases. Simultaneously,the bonding characteristics and plasticity are improved,and the bending strength is raised to 891 MPa. The fracture morphology shows a good bonding between coating and substrate,and also a combination of cleavage fracture and dimple fracture.更多还原