激光熔覆裂纹的形成机理及控制方法

Forming Mechanism and Controlling Method of Laser Cladding Crack

激光熔覆技术是利用激光辐射使熔覆材料和基体表面同时熔化并快速凝固、从而显著改善基体材料物理性能的一种新工艺方法。但激光熔覆工艺的选择不当则会使熔覆层产生裂纹、气孔、未熔合等,从而影响熔覆制件的综合性能。本文研究了激光熔覆裂纹的种类以及熔覆层的应力类型,分析了裂纹产生的机理,指出材料间热膨胀系数、弹性模量的明显差别及激光熔池区域的温度梯度所决定的热应力是熔覆层裂纹形成的根源。并从熔覆材料和基体材料的合理选择、成形工艺参数的合理设计及热处理等方面,阐述了熔覆裂纹的影响因素和控制方法。

Laser cladding is a new surface strengthening technology which uses laser radiation to make coating materials and the surface of substrate melted and rapidly solidified. The technology can significantly improve physical performance of the substrate materials. However, such as crack, pore, and ill bonding between cladding layers might appear if the process parameters are controlled improperly and the comprehensive performance of the laser cladding parts will be influenced. The laser cladding cracks and the stress styles are classified, the forming mechanism of the cracks produced in the laser cladding layer is deeply analyzed. The root of the cladding cracks is formed by the obvious difference of thermal expansion coefficient and elastic modulus of the materials and the thermal stress determined by temperature gradient of the laser molten pool. The influencing factors of the cladding cracks and the way of preventing from cracks in laser cladding layer is discussed including the cladding materials and substrate materials, the parameters of cladding process and heat treatment.