The effects of coating thickness on the fatigue lives of AISI 1045 steel shaft-bending specimens with WC-10%Co-4%Cr high-velocity oxygen fuel (HVOF) coatings and hard chrome electroplated coatings under cyclic loading conditions are investigated. Residual stress distributions of the HVOF-coated layer and the hard chrome-plated layer were measured. During cyclic fatigue testing, cracks are initiated near the interface between the HVOF coating and the steel substrate and propagate through the substrate to cause final fracture based on experimental results. For the specimens with hard chrome-plated coatings, the fatigue crack is initiated near the top of the coating, propagates through the coating, and then grows in the thickness direction of the steel substrate to cause final fracture. As the coating thickness of the HVOF-coated specimens increases, the fatigue strength of the specimens increases, which can be attributed to the fact that the magnitude of the compressive residual stress near the interface between the substrates and the HVOF coatings is higher when the coating thickness gets higher. As for the hard chrome-plated specimens, the fatigue strength is deteriorated when the coating thickness is increased. The microcrack density in the hard chrome coatings increases with the coating thickness and, therefore, may result in the decreased fatigue strength.

中文翻译：

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涂层厚度对 AISI 1045 钢 HVOF 热喷涂和硬铬电镀疲劳行为的影响

研究了涂层厚度对具有 WC-10%Co-4%Cr 高速氧燃料 (HVOF) 涂层和硬铬电镀涂层的 AISI 1045 钢轴弯曲试样在循环载荷条件下疲劳寿命的影响。测量了 HVOF 涂层和硬铬镀层的残余应力分布。在循环疲劳测试过程中，根据实验结果，在 HVOF 涂层和钢基体之间的界面附近产生裂纹，并通过基体传播，导致最终断裂。对于镀硬铬涂层的试样，疲劳裂纹在涂层顶部附近开始，通过涂层传播，然后在钢基体的厚度方向上扩展，导致最终断裂。随着 HVOF 涂层试样的涂层厚度增加，试样的疲劳强度增加，这可以归因于随着涂层厚度的增加，基体和HVOF涂层之间界面附近的压残余应力的大小更高。对于镀硬铬试样，涂层厚度增加时疲劳强度下降。硬铬涂层中的微裂纹密度随着涂层厚度的增加而增加，因此可能导致疲劳强度降低。当涂层厚度增加时，疲劳强度会变差。硬铬涂层中的微裂纹密度随着涂层厚度的增加而增加，因此可能导致疲劳强度降低。当涂层厚度增加时，疲劳强度会变差。硬铬涂层中的微裂纹密度随着涂层厚度的增加而增加，因此可能导致疲劳强度降低。