激光熔覆工艺参数对CBN膜层裂纹率的影响

在TC11表面激光熔覆制备CBN膜层，通过研究激光工艺参数与裂纹率关系，控制熔覆层裂纹的产生。采用正交试验，并利用ANSYS软件平台对温度梯度进行研究，利用SEM、EDS对熔覆层截面形貌和成分进行分析。结果表明：对于熔覆层宏观裂纹，随着激光能量密度的增大，裂纹率明显下降，熔覆层质量变好，在激光能量密度为6×104 J/cm2送粉率为1 r/s时涂层质量较好；随着扫描速度增大时，裂纹率呈上升趋势，在扫描速度为3 mm/s、送粉率为1 r/s时裂纹率较小；随着送粉率增加，裂纹率先增加后减小，在送粉率为2.25 r/s、激光能量密度为3.4×104 J/cm2达到最大。对于熔覆层微观裂纹，随着激光功率增加，裂纹率先减小后增加，激光功率为1 800 W时，裂纹率达到最低；随着扫描速度增加，裂纹率也是先减小再增加，扫描速度为4 mm/s时，裂纹率达到最低。经过SEM与EDS分析，通过调整激光熔覆工艺参数，控制熔覆过程中温度场的温度梯度，进而控制熔覆层的裂纹率，可以获得形貌与组织成分良好的涂层。

Relationship Between Crack Rate of CBN Coating and Parameters of Laser Cladding

Laser cladding technique was used to prepare CBN film on the surface of TC11, the relationship between laser parameters and crack rate was studied to control cracks of the cladding layers. ANSYS software was used to study the temperature gradient by orthogonal experiments, and the morphology and component of cladding layer section were analyzed by SEM and EDS observation. Results show that the macro crack rate significantly decreases with the increase of laser energy density, resulting in a better cladding layer, and the optimized parameters are the laser energy density of 6×104 J/cm2 and the powder feed rate of 1 r/s. Crack rate increases with the increase of the scanning velocity, which is relative lower under scanning velocity of 3 mm/s and powder feed rate of 1 r/s. Crack rate increases first and then decreases with the increase of the powder feed rate, reaching a peak value under a powder feed rate of 2.25 r/s and laser energy density of 3.4×104 J/cm2. As to the micro crack of the cladding layer, the crack rate decreases first and then increases with the increase of the laser power and scanning velocity, reaching a minimum value at laser power of 1800 W and scanning velocity of 4 mm/s . SEM and EDS analysis showes that the crack rate can be restrained and the layer with good morphology and component can be obtained by adjusting of the laser cladding parameters and controlling the temperature gradient.