目的 针对工作温度较低（低于550 ℃）的热作模具，研究热喷涂20%NiCr-80%Cr3C2涂层在5CrNiMo热作模具钢基体上的抗热冲击和抗氧化性能。方法 利用超音速火焰喷涂技术（HVOF）在5CrNiMo热作模具钢基体上制备20%NiCr-80%Cr3C2涂层。采用维氏显微硬度计和万能力学试验机分别测试涂层表面的显微硬度和结合强度；采用管式炉研究涂层在250~550 ℃之间的抗循环热冲击及抗氧化性能；采用光学显微镜、扫描电子显微镜、能谱仪和X射线衍射仪分析表征涂层经循环热冲击试验前后样品的形貌、组织结构及物相组成。结果 20%NiCr-80%Cr3C2涂层组织均匀致密，具有极高的表面显微硬度（818.9HV）和结合强度（64.0 MPa）。200次循环热冲击后，涂层内部产生了微裂纹，但并未相互连通，样品表面依旧保持光洁平整，且粘接相中析出的碳化物颗粒使涂层硬度大幅提高（1029.0HV）。涂层与基体界面形成了Fe和Cr元素的氧化物层，但其厚度增至约1 μm后处于稳定阶段，且该氧化层连续致密，与基体和涂层结合良好，并未表现出使涂层剥离的倾向。结论 利用HVOF制备的20%NiCr-80%Cr3C2涂层抗循环热冲击性能良好，且能够有效提高5CrNiMo热作模具钢工作表面的硬度和抗氧化性能。

The work aims to study the thermal shock resistance and antioxidant properties of thermal sprayed 20%NiCr-80%Cr3C2 coating on 5CrNiMo die steel substrate for hot die with low operating temperature (below 550 ℃). The 20%NiCr-80%Cr3C2 coating was produced on 5CrNiMo die steel substrate by high velocity oxy-fuel (HVOF). The hardness and bonding strength of the coating were tested by Vickers microhardness tester and universal mechanical testing machine. The anti-cyclic thermal shock properties of the coating between 250 ℃ and 550 ℃ were investigated by vacuum tube furnace. The morphology, microstructure and phase composition of the coatings before and after the cyclic thermal shock test were characterized by optical microscopy, scanning electron microscope (SEM), energy dispersive spectrum (EDS) and X-ray diffraction (XRD), respectively. 20%NiCr-80%Cr3C2 coating prepared by HOVF was uniform and dense, with extremely high surface microhardness (818.9HV) and bonding strength (64.0 MPa). After 200 times of cyclic thermal shock, microcracks appeared inside the coating, but were not connected to each other, and the surface of the sample still remained smooth. The carbide particles precipitated in the binding phase greatly increased the hardness of the coating (1029.0HV). The oxide layer of Fe and Cr was formed at the interface between the coating and the substrate. However, the layer reached in a stable stage when the thickness increased to 1 μm, and it was continuously dense and well bonded to the substrate and the coating, and did not show the tendency to peel off from the coating. Therefore, the 20%NiCr-80%Cr3C2 coating produced by HVOF has good anti-cyclic thermal shock properties, and can effectively improve the hardness and antioxidant properties of 5CrNiMo hot die steel working surface.