为了进一步提高模具钢表面的硬度和耐磨性能, 以Cr12MoV作为基体材料, 利用2 kW半导体激光器, 以同轴送粉的方式在其表面上熔覆高硬度的Fe基合金粉末。通过光学显微镜、X射线衍射、扫描电镜分析熔覆层的组织形貌和物相; 用显微硬度计测试熔覆层的显微硬度, 用磨损试验机进行耐磨试验。进而研究激光功率、扫描速度和送粉量等工艺参数对熔覆层组织性能的影响, 确定了最优化工艺参数。实验结果表明, 使熔覆层的硬度和耐磨性较优良的工艺参数为: 激光功率为1.2 kW, 扫描速度为720 mm/s, 送粉量为8.5 g/min。在此工艺参数下, 熔覆层无裂纹、气孔、夹渣等缺陷, 且显微硬度和耐磨性能得到显著提高, 最高硬度达921 HV0.2, 熔覆层的磨损失重仅为基体材料的25%, 明显高于基体的硬度和耐磨性, 这归因于熔覆层中存在V4C3、Cr23C6、Cr7C3等细小树枝晶。

In order to further improve the surface hardness and wear resistance of the mould steel, Fe-based alloy powder was cladded on the surface of Cr12MoV mould steel by 2 kW diode laser with coaxial powder feeder. The microstructure and phase structure of coating were analyzed by OM, XRD, SEM, the microhardness and wear resistance were examined by microhardness tester and pin-on-disc wear tester. The influences of the laser power, scanning speed and feeding powder rate on performance of the coatings were studied and then the optimized parameters were obtained. The results show that the microhardness and wear are behavior of the optimal laser cladding conditions with the laser power of 1.2 kW, a scanning speed of 720 mm/s a feeding powder rate of 8.5 g/min. Laser cladding coating without any defects, such as cracks, porosity, inclusions, was achieved though the optimal processing parameter. The maximum hardness is 921 HV0.2 and the weight loss of coating is equal to 25% of that of the substrate. So, the microhardness and the wear resistance of the laser cladding coating significantly increase because of finer dentrite V4C3, Cr23C6, Cr7C3.