Laboratory Soete, Ghent University, Ghent, Belgium.
Department of Fusion Science and Technology, Sun Moon University, Asan-si, Korea.
Sci Rep. 2023 Jan 24;13(1):1308. doi: 10.1038/s41598-023-28128-8.
Alloy 718 is commonly used in the maritime and aerospace industries due to its strength and durability, particularly in engine rotating components such as disks, fan blades, and high-pressure compressors. As a new type of 3D printing technology, directed energy deposition (DED) can employ lasers to melt metal powders or wires to fabricate arbitrary-shaped workpieces directly from customized data, thereby making machining more synergistic and intuitive. However, the surface properties of the DED-printed alloy 718 samples, such as surface roughness and wear resistance, are typically subpar. By introducing severe plastic deformation to the near-surface, ultrasonic nanocrystal surface modification (UNSM) can be used as a post-processing method and results in altered properties. The uniaxial tensile test reveals that the UNSM-treated alloy 718 exhibits a higher mechanical property. Moreover, using a fretting test rig in accordance with the cylinder-on-plane agreement, a higher wear resistance for UNSM-treated alloy 718 is observed. This study employs the finite element method to fully comprehend the effect of UNSM on wear performance. The fretting wear process of Inconel 718 alloy is established using an energy-based finite element model. Considering the severe practical scenarios, the Johnson-Cook constitutive model is implemented, with the linear isotropic hardening model capturing the plastic behavior. In comparison to experimental measurements, the finite element results demonstrate unprecedented wear loss consistency with an error of less than 2%. Therefore, we conclude that the finite element model built in this study exhibits a high accuracy and can be used to analyze the effect of UNSM on fretting wear behavior. According to finite element analysis, as the normal load increases, the improvement in wear resistance induced by UNSM decreases. Given that the finite element model is based on the energy method, the effects of coefficient of friction (COF) and wear coefficient modified by UNSM are investigated separately. According to the findings, the UNSM-modified COF and wear coefficient play a significant role in determining the wear characteristics. Due to the removal of a substantial amount of material from the central area of the alloy 718 surface by wear, it is also possible to observe that severe plastic strains are primarily concentrated at the edges of the wear scars.
因强度和耐用性，尤其是在发动机旋转部件如盘、风扇叶片和高压压缩机中，Alloy 718 常用于航海和航空航天工业。作为一种新型的 3D 打印技术，定向能量沉积（DED）可以使用激光将金属粉末或线材熔化，直接从定制数据制造任意形状的工件，从而使加工更协同、更直观。然而，DED 打印的 Alloy 718 样品的表面性能，如表面粗糙度和耐磨性，通常较差。通过在近表面引入剧烈塑性变形，可以将超声纳米晶表面改性（UNSM）作为一种后处理方法，从而改变性能。单向拉伸试验表明，经 UNSM 处理的 Alloy 718 具有更高的机械性能。此外，使用根据圆柱-平面协议的微动试验台，观察到经 UNSM 处理的 Alloy 718 的耐磨性更高。本研究采用有限元法全面理解 UNSM 对磨损性能的影响。采用基于能量的有限元模型建立了 Inconel 718 合金的微动磨损过程。考虑到实际情况严重，采用 Johnson-Cook 本构模型，线性各向同性硬化模型捕获塑性行为。与实验测量相比，有限元结果显示磨损损失的一致性前所未有，误差小于 2%。因此，我们得出结论，本研究中建立的有限元模型具有很高的准确性，可以用来分析 UNSM 对微动磨损行为的影响。根据有限元分析，随着法向载荷的增加，UNSM 引起的耐磨性提高会降低。由于有限元模型基于能量法，分别研究了 UNSM 修正的摩擦系数（COF）和磨损系数的影响。结果表明，UNSM 修正的 COF 和磨损系数对确定磨损特性起着重要作用。由于磨损会从 Alloy 718 表面的中心区域去除大量材料，因此也可以观察到严重的塑性应变主要集中在磨损痕迹的边缘。
