The effect of cold spray coating parameters on the fatigue life and cracking mechanism of AZ31B-H24 coated with AA7075 powder is investigated. Two sets of coated samples are fabricated based on the selection of different coating parameters. An in-situ control of heat transfer is performed to obtain different residual stress states and microstructure at the aluminum/magnesium interface. Subsequently, the samples are tested under load-controlled fatigue tests at different load amplitudes. Fatigue lives are obtained and the cracking behavior of the two samples is studied and compared with that of uncoated baseline samples. It is revealed that the samples with compressive residual stress at the coating/substrate interface have significantly longer lives (approximately 85% improvement at the same stress) compared with that of the baseline samples. In contrast, samples with tensile residual stress at the interface have similar or slightly improved lives (approximately 24%) compared with that of the baseline samples. The cracking mechanisms of these two samples are considerably different. In the case of compressive samples, cracks initiate at the coating surface and propagate through the splat boundaries of the cold spray coating to the substrate. Conversely, in the case of tensile samples, delamination and cracking initiate at the interface and subsequently propagate to the substrate and through the splats in the coating. The different lives and cracking mechanisms obtained are attributed to the differences in the initial state of stress, details of the microstructure of the nano-size interface layer, and the morphology of the substrate grains adjacent to the interface.

研究了冷喷涂参数对AA7075粉末涂层AZ31B-H24疲劳寿命和开裂机理的影响。根据不同涂层参数的选择，制作了两组涂层样品。执行传热的原位控制以获得铝/镁界面处不同的残余应力状态和微观结构。随后，样品在不同载荷幅值的载荷控制疲劳试验下进行测试。获得了疲劳寿命，研究了两个样品的开裂行为，并与未涂层的基线样品进行了比较。结果表明，与基线样品相比，在涂层/基材界面处具有压缩残余应力的样品具有显着更长的寿命（在相同应力下提高约 85%）。相比之下，与基线样品相比，在界面处具有拉伸残余应力的样品具有相似或略微提高的寿命（约 24%）。这两个样品的开裂机制有很大不同。在压缩样品的情况下，裂纹从涂层表面开始，并通过冷喷涂涂层的飞溅边界传播到基材。相反，在拉伸样品的情况下，分层和开裂在界面处开始，随后传播到基材并通过涂层中的碎片。获得的不同寿命和开裂机制归因于初始应力状态、纳米尺寸界面层微观结构细节以及界面附近基体晶粒形态的差异。与基线样品相比，在界面处具有拉伸残余应力的样品具有相似或略微提高的寿命（约 24%）。这两个样品的开裂机制有很大不同。在压缩样品的情况下，裂纹从涂层表面开始，并通过冷喷涂涂层的飞溅边界传播到基材。相反，在拉伸样品的情况下，分层和开裂在界面处开始，随后传播到基材并通过涂层中的碎片。获得的不同寿命和开裂机制归因于初始应力状态、纳米尺寸界面层微观结构细节以及界面附近基体晶粒形态的差异。与基线样品相比，在界面处具有拉伸残余应力的样品具有相似或略微提高的寿命（约 24%）。这两个样品的开裂机制有很大不同。在压缩样品的情况下，裂纹从涂层表面开始，并通过冷喷涂涂层的飞溅边界传播到基材。相反，在拉伸样品的情况下，分层和开裂在界面处开始，随后传播到基材并通过涂层中的碎片。获得的不同寿命和开裂机制归因于初始应力状态、纳米尺寸界面层微观结构细节以及界面附近基体晶粒形态的差异。