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激光钎涂金刚石的涂层形成行为及其机理分析

Analysis of the formation behavior and mechanisms of diamond coatings through laser brazing

  • 摘要: 利用激光热源进行金刚石钎涂研究,并借助高速摄像对金刚石涂层成形行为及其机理进行分析. 结果表明,在没有金刚石的情况下,钎料粉末的熔合铺展过程可分为粉末熔化、液态钎料聚合、粉末吸附熔合、润湿铺展和涂层凝固成形5个阶段,表面张力最小的位置处于熔池中心,而表面张力最大的位置处于熔池边缘,熔池中存在表面张力梯度,是熔池流动的主要驱动力;涂层中加入金刚石,涂层成形经历比未加入金刚石多出一个阶段,即金刚石迁移至涂层表层阶段,位于钎料润湿铺展阶段之后,钎涂过程中,金刚石趋向于沿着熔体表面边缘上浮,这主要是由于金刚石与液态钎料之间的界面张力远大于与固态基体界面张力,还有Stokes力、重力、浮力、Basset力等综合作用所致;钎涂过程中,金刚石透射激光的高效低损伤热作用特性会有效避免金刚石在钎涂过程中的过热损伤,这是金刚石激光钎涂层的最大潜在优势.

     

    Abstract: Research on diamond coatings was conducted using laser heating as a heat source, and the behavior and mechanisms of diamond coating formation were analyzed with the assistance of high-speed cameras. The results show that in the absence of diamonds, the brazing powder's fusion and spreading process can be divided into five stages: powder melting, liquid brazing material aggregation, powder adsorption fusion, wetting and spreading, and coating solidification. The minimum surface tension is located at the center of the weld pool, while the maximum surface tension is found at the weld pool's edges. A surface tension gradient in the weld pool is the main driving force behind its flow. After introducing diamonds into the coating, the formation process of the coating goes through six stages: powder brazing material melting, liquid brazing material aggregation, brazing material micro-powder adsorption fusion, brazing material wetting and spreading, migration of diamonds to the surface of the coating, and coating solidification. During the diamond brazing and coating process, diamonds tend to float along the surface edge of the weld pool. This is primarily due to the interface tension between diamonds and liquid brazing material being much greater than that between diamonds and the solid substrate, along with the combined effects of Stokes force, gravity, buoyancy, Basset force, and others. Additionally, the efficient and low-damage thermal effect of laser transmission during the brazing process helps to prevent overheating damage to the diamonds. This is a significant potential advantage of diamond-enhanced coatings produced through laser brazing.

     

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