激光熔覆H13钢的裂纹敏感性及形成机理

采用同轴送粉激光熔覆方法在H13钢基体上多道搭接熔覆H13钢,用光学显微镜、SEM和XRD对熔覆层的组织特征进行分析,用着色渗透法检验熔覆层裂纹,通过图像处理定量表征裂纹密度,研究了工艺参数对裂纹敏感性的影响,并分析研究了裂纹形成机制。结果表明,H13钢激光熔覆层的组织主要由枝晶状奥氏体转变的马氏体和残留奥氏体组成;熔覆层裂纹敏感性较大,主要是热裂,裂纹在奥氏体柱状枝晶间萌生并扩展;激光功率对裂纹敏感性影响大,功率越大裂纹敏感性越低,优化工艺参数可以获得无裂纹缺陷熔覆层。

Crack sensitivity and formation mechanism of laser clad H13 steel

A multitrack overlapping clad layer was fabricated on H13 steel substrate by laser cladding with coaxial powder feeding, the microstructure characteristics were studied by means of optical microscope (OM), SEM and XRD. The clad layer cracks were detected by penetrant inspection method, and the crack density was quantitatively characterized by image processing. The effects of the laser cladding process parameters on crack sensitivity were studied, and the mechanism of crack formation was analyzed. The results show that the microstructure of H13 steel clad layer is mainly composed of martensite and residual austenite transformed from dendrite-like austenite. The crack sensitivity of the clad layer is high, most of them are thermal cracks, which initiates and propagates between austenite columnar dendrites. The laser power has a significant impact on the crack sensitivity of the clad layer, the higher the power, the lower the crack sensitivity, and the clad layer without cracks can be obtained by optimizing process parameters.