激光熔覆Inconel718合金裂纹分析及裂纹控制研究

Crack Analysis and Control of Laser Cladding Inconel718 Alloy

目的针对K418合金表面激光熔覆裂纹萌生、元素偏析等难题,探究裂纹萌生与元素偏析之间的关系,利用后处理工艺进行裂纹的修复及偏析现象的控制。方法在K418合金表面激光熔覆了Inconel718合金,以基体及熔覆材料的热物性参数和界面元素匹配性为出发点,对熔覆中裂纹的敏感性进行了分析。结果合金元素的偏析造成了裂纹的萌生与扩展。基体热影响区裂纹的形成与热影响区内析出的块状碳氮化物有关,熔覆层裂纹与枝晶间析出的不规则链状Laves相有关。采用激光重熔工艺对熔覆层进行了后处理,试验结果表明,重熔后的组织致密,晶粒细小均匀,无裂纹及粘粉等明显缺陷。激光重熔减少了基体热影响区及熔覆层中因元素偏析产生的碳氮化物及Laves相的尺寸及数量,重熔后覆层的摩擦因数为0.55,比重熔前下降了49.5%,具有良好的减摩特性;磨损率为3.15×10^−4 mm^3/(N·mm),比重熔前下降了37.5%,耐磨性能得到提升。结论激光重熔技术可以愈合K418激光熔覆Inconel718合金的裂纹,并显著降低涂层的元素偏析程度。

The work aims to explore the relationship between crack initiation and element segregation for the problems of laser cladding crack initiation and element segregation on K418 alloy surface and then repair the crack and control the segregation by the post-treatment process.The Inconel718 alloy was deposited on the surface of K418 alloy by laser cladding.The sensitivity of the crack during the cladding was analyzed based on the thermal properties of the matrix and the cladding material and the interface element matching.The segregation of alloy elements caused the initiation and propagation of cracks.The formation of thermal cracks in the matrix was related to the massive carbonitrides precipitated in the heat-affected zone,and the cracks of cladding layer were related to the irregular chain Laves phase precipitated between dendrites.The cladding layer was post-treated by laser remelting process.The test results showed that the microstructure after remelting was dense,the grains were fine and uniform,and there were no obvious defects such as cracks and sticky powder.The size and quantity of carbonitride and Laves phase due to element segregation in the heat affected zone and the cladding layer of the matrix were reduced.The friction coefficient of the cladding after remelting was 0.55,and the specific gravity was reduced by 49.5%before melting,which showed good antifriction.The wear rate was 3.15×10^−4 mm^3/(N·mm),the specific gravity was decreased by 37.5%before melting,and the wear resistance was improved.Laser remelting technology can heal the crack of Inconel718 alloy on K418 by laser cladding and significantly reduce the degree of elemental segregation of the coating.