Hard nano-multilayered TiAlCrN/NbN coatings on cemented carbide have shown promise in dry high speed machining applications involving repetitive contact, such as end milling of hardened H13 steel. In this study the fracture resistance of TiAlCrN/NbN coatings under repetitive dynamic high strain rate loading has been evaluated by the micro-scale impact test method. Although the fatigue mechanisms can vary with the ratio of coating thickness t to the indenter radius R, macro-scale tests of thin coatings using probe radii in the mm range are necessarily at low t/R. Micro-impact tests at higher t/R have been performed with a range of diamond indenter geometries (R = 8, 20, 100 μm) to investigate the role of varying t/R (0.03–0.375) on the deformation behaviour. With the largest radius probe there was no clear failure for the coatings or substrate under the test conditions. With the 8 and 20 μm radius probes the behaviour of the coatings was strongly load-dependent and they were more susceptible to impact-induced damage than the carbide substrate. As the load increased there was a change from coating to substrate dominated deformation behaviour as the stress field extended further into the substrate. At lower load the dominant fracture behaviour was coating fracture through ring cracking, radial cracking and chipping. At higher load chipping became less prevalent and break-up of the carbide substrate more extensive.

硬质合金多层TiAlCrN / NbN硬质多层涂层在涉及重复接触的干式高速机加工应用中表现出了希望，例如淬硬H13钢的端铣削。在这项研究中，TiAlCrN / NbN涂层在反复动态高应变速率载荷下的抗断裂性能已通过微型冲击试验方法进行了评估。尽管疲劳机制会随涂层厚度t与压头半径R的比值而变化，但使用mm范围内的探查半径对薄涂层进行宏观测试必须在低t / R的条件下进行。在较高的t / R下进行了微冲击测试，测试范围为各种金刚石压头几何形状（R = 8、20、100μm）以研究变化的t / R（0.03-0.375）对变形行为的作用。使用最大半径的探针，在测试条件下，涂层或基材没有明显的故障。使用半径为8和20μm的探针，涂层的性能与载荷密切相关，并且与碳化物基体相比，它们更容易受到冲击引起的破坏。随着载荷的增加，随着应力场进一步延伸到基体中，从涂层到基体的变形行为发生了变化。在较低的载荷下，主要的断裂行为是由于环裂，径向裂纹和碎裂引起的涂层断裂。在较高的负载下，切屑变得不那么普遍，碳化物基体的破裂更广泛。