为了避免激光熔覆时熔覆层边界处产生过烧和塌陷等缺陷, 基于热传导理论分析了基体不同位置的散热差异, 采用数值计算方法分析扫描路径对温度场的影响, 在激光功率1000W、扫描速率5mm/s、送粉量9.15g/min、扫描间距1.5mm、基体尺寸40mm×30mm×7mm时, 同向熔覆和异侧熔覆比反向熔覆和同侧熔覆边界熔池温度分别降低约300℃和500℃, 预测了反向熔覆和同侧熔覆的过烧和塌陷区域并进行了实验验证。结果表明, 扫描路径对边界过烧和塌陷的影响很大, 同向熔覆和异侧熔覆可以在保证高加工效率、材料利用率以及合理工艺参量的同时提高边界熔覆质量; 异侧熔覆可以更好地平衡热量累积与散热间的关系, 使熔覆层边界晶粒细密、内部组织分布均匀、性能更加优良。此项研究对提高激光熔覆层质量是有帮助的。

In order to avoid defects such as overburning and collapsing at the boundary of laser cladding layer, difference of heat dissipation at different positions of the substrate was analyzed based on the theory of heat conduction. The influence of scanning path on temperature distribution was studied by numerical calculation. With the parameters of laser power 1000W, scanning speed 5mm/s, powder feeding quantity 9.15g/min, scanning interval 1.5mm and substrate size 40mm×30mm×7mm, molten pool temperature of boundary under the same direction cladding and different side cladding is about 300℃ and 500℃ lower than that under different direction cladding and the same side cladding respectively. Overburning and collapsing regions under different direction cladding and the same side cladding are predicted and experimentally verified. The results show that the scanning path has a great influence on the overburning and collapsing of boundary. The same direction cladding and different side cladding can improve the cladding quality of boundary without changing machining efficiency, material utilization ratio and the rationality of process parameters. Different side cladding can balance the relationship between heat accumulation and heat dissipation better, which can refine the grain of boundary, make internal microstructure uniform and increase the performance of cladding layer. This study is helpful to improve the quality of laser cladding layer.