激光熔覆裂纹产生机理及控制方法分析

激光熔覆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的工艺方法。熔覆工艺的选择不当会使熔覆层产生裂纹,降低熔覆制件抗疲劳的能力。本文研究了高能激光束和材料的作用特点以及熔覆层的应力类型,分析了熔覆层裂纹的形成机理,建立了热应力的计算模型,从熔覆材料和基体材料的选择、数值模拟技术预测以及利用熔覆层应力的作用特点改进熔覆工艺三个方面阐述了裂纹的影响因素和控制方法。

Investigation of Generation Mechanism and Controlling Method of Cladding Layer ranking by laser cladding

Laser cladding is a new surface strengthening technology which uses laser radiation to let coating materials and the surface of substrate melt simultaneous. The technology can significantly improve physical performance of the substrate materials. However, such defect as crack, pore, and ill bonding between cladding layers might appear if the process parameters controlled improperly and the crack of cladding layers decrease fatigue resistance of the laser cladding parts. The interaction characteristic between laser beam with cladding materials and stress style in the cladding layers is studied, the forming mechanism of the crack producing in the laser cladding process is deeply analyzed, and the mathematical model of thermal stress is established. The three preventive measures of the cracking behavior, including the choice of cladding materials and substrate, the forecast of numerical simulated technology and the improvement cladding process using the character of the stress in the cladding layer, are discussed.