为了对H13模具钢进行更好的强化和修复，在H13钢基体上采用激光熔覆制备了H13/Ni/WC混合粉末双层梯度熔覆层，在两层熔覆层的初始粉末中，Ni/WC混合粉末的质量分数分别为15%和30%。测试并比较了基体与熔覆层的显微硬度、高温硬度、热疲劳性能和耐磨损性能，探讨了熔覆层的磨损机理。熔覆层横截面的显微硬度从基体到熔覆层外表面呈明显的梯度分布规律，接近熔覆层外表面区域的显微硬度为1100 HV，而基体的显微硬度仅为400 HV。高温硬度测试结果表明：随着测试温度升高，基体和接近熔覆层外表面区域的硬度均下降，且熔覆层下降的幅度大于基体，室温时基体和熔覆层的硬度分别为1347.68 HV和1510.35 HV；当测试温度达到800 ℃时，基体和熔覆层的硬度分别下降到1006.8 HV和921.4 HV；当测试温度为500 ℃左右时，两区域的硬度相当。耐磨性测试结果表明：当测试温度在500 ℃以下时，熔覆层的耐磨性优于基体；当测试温度在500 ℃及以上时，熔覆层的耐磨性低于基体。主要原因是当测试温度低于500 ℃时，熔覆层中马氏体的强度和硬度很高，使得熔覆层较基体具有更高的硬度；但当测试温度高于500 ℃时，会发生退火现象，从而导致熔覆层表面的硬度和耐磨性急剧下降。

To substantially strengthen and repair H13 die steel， an H13/Ni/ WC hybrid powder double-layer gradient cladding layer is prepared herein through laser cladding on an H13 steel matrix. The contents of the Ni/WC mixed powder in the initial powder of two cladding layers are 15% and 30%， respectively. Furthermore， the microhardness， high temperature hardness， thermal fatigue properties， and wear resistance of the matrix and cladding layer are tested and compared. Similarly， the wear mechanism of the cladding layer is discussed. The microvickers hardness of the cladding layer cross-section shows a gradient distribution from the matrix to the outer surface of the cladding layer. The average microhardness near the outer surface of the cladding layer is 1100 HV， whereas the average microhardness of the matrix is 400 HV. Results of the high temperature hardness test reveal that an increase in the test temperature decreases the vickers hardness of the matrix and area near the outer surface of the cladding layer. Moreover， the decrease extent of the cladding layer is larger than that of the matrix， which are 1347.68 HV and 1510.35 HV， respectively， at room temperature. Furthermore， when the test temperature reaches 800 ℃， the hardness of the matrix and the cladding layer drop to 1006.8 HV and 921.4 HV， respectively. When the test temperature is about 500 ℃， the hardness values of the two regions are observed to be equal. The wear resistance test also show that the wear resistance of the cladding layer is better than that of the matrix below 500 ℃， whereas the wear resistance of the cladding layer is lower than that of the matrix at 500 ℃ or above. This is attributed to the fact that when the temperature is below 500 ℃， the martensite in the cladding layer exhibits extremely high strength and hardness， leading to higher hardness of the cladding layer than that of the matrix. Conversely， when the temperature is above 500 ℃， the surface hardness and wear resistance of the cladding layer sharply decrease owing to the annealing phenomenon.