热喷涂零件界面裂纹扩展行为影响因素研究

热喷涂技术在提高构件寿命等方面得到了广泛应用,但界面裂纹的存在对零件寿命的影响尤其明显。本工作利用有限元法研究了残余应力、涂层厚度以及初始裂纹长度等因素对界面裂纹扩展的影响。研究结果表明:残余压应力的增加会导致临界载荷的降低,促使裂纹尖端应力相角增大,更易萌生界面裂纹;而残余拉应力的增加会导致临界载荷的升高,促使裂纹尖端应力相角降低,更易萌生垂直于界面的裂纹。此外,厚涂层易产生平行于界面的裂纹,以剪切失效为主导;薄涂层易产生垂直于界面的裂纹,以拉伸失效为主导。初始裂纹长度越长越易出现涂层与基体的剥离,导致涂层的失效。通过三点弯曲实验对不同初始长度的裂纹进行验证,实验结果与有限元模拟结果相近,验证了有限元模拟的正确性,为精确控制热喷涂零件界面的裂纹扩展提供了科学依据和理论基础。

Research on the Influence Factors of the Interfacial Crack Propagation Behavior of Thermal Spraying Parts

Thermal spraying technology has been widely used in improving the life of components, but the existence of interface cracks has an obvious effect on the life of parts. In this paper, the effects of residual stress, coating thickness and initial crack length on the interface crack propagation were studied by using the finite element method. The result showed that the increase of residual compressive stress leaded to the decrease of the critical load and the increase of the phase angle of the crack tip, which was more likely to have the interface crack. The increase of residual stress could result in the increase of critical load and the decrease of the stress phase angle of the crack tip, which was more prone to generate cracks perpendicular to the interface. At the same time, the interface crack in the thick coating was the main crack mode, and was mainly shear failure. Thin coating was easy to produce cracks perpendicular to the interface, with tensile failure as the leading. The longer the initial crack length, the more prone to peeling of the coating and the substrate, resulting in failure of the coating. The three point bending test was used to verify the crack with different initial length, and the experimental results were similar to the finite element simulation results, which verified the correctness of the finite element simulation, and provided a scientific basis and theoretical basis for the accurate control of the interface crack propagation of the thermal spraying parts.