© 2020 Elsevier B.V. Abrasive waterjet (AWJ) is widely used for machining of advanced (e.g. nickel-based) superalloys as it offers high material removal rates and low cutting temperatures. However, the inadequate surface integrity, e.g. large number of scratches and embedded particles in the machined surface, which would induce severe deteriorations of the materials functional performance, has been one of the greatest issues of the AWJ machining technique. To solve this problem, this research proposed a dual-process abrasive waterjet machining method, whereby two different functions of abrasive waterjet were employed: materials removal (first process) and surface modification (secondary process), hence, to improve the workpiece surface integrity. Two types of entrained particles, i.e. with sharp cutting edges (e.g. garnet) and smooth surfaces (e.g. stainless steel ball), that depending on their kinetic energy density can either cut or modify the workpiece surface respectively, are employed for these the two constitutive processes of the proposed dual-waterjet machining method. A critical standoff distance and inclination angle of the waterjet nozzle has been defined for the surface modification process thus, to eliminate the embedded particles and scratches left by the first cutting process while also introducing a surface strengthening effect. To support this approach, a mathematical model has been proposed for determining the surface modification parameters (e.g. jet feed speed and abrasive flow rate). In-depth analysis of the microstructural and metallurgical alternations of the machined workpiece surface and superficial layer have also been conducted to reveal the mechanisms responsible for the surface damage elimination and surface strengthening. Moreover, a four point bending fatigue test has been conducted to validate the mechanical performance, whereby a significant improvement of the fatigue life on the machined workpiece was achieved when compared with the case that single AWJ cutting method (91 %) and conventional machining (34 %) are employed. This proves that the proposed dual-processing AWJ machining method is of high efficiency to improve the functional performance of components on a single machine tool platform.

中文翻译：

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磨料水刀双加工——一种镍基高温合金的加工和表面改性方法

© 2020 Elsevier BV 磨料水刀 (AWJ) 广泛用于加工高级（例如镍基）高温合金，因为它具有高材料去除率和低切削温度。然而，表面完整性不足，例如加工表面有大量划痕和嵌入颗粒，这会导致材料功能性能的严重恶化，一直是 AWJ 加工技术的最大问题之一。为了解决这个问题，本研究提出了一种双工艺磨料水刀加工方法，利用磨料水刀的两种不同功能：材料去除（第一道工序）和表面改性（第二道工序），从而提高工件表面完整性。两种类型的夹带颗粒，即具有锋利切削刃（例如石榴石）和光滑表面（例如 不锈钢球），根据它们的动能密度可以分别切割或修改工件表面，被用于所提出的双水刀加工方法的这两个本构过程。为表面改性过程定义了水刀喷嘴的临界间距和倾斜角，从而消除第一次切割过程中留下的嵌入颗粒和划痕，同时引入表面强化效果。为了支持这种方法，已经提出了用于确定表面改性参数（例如射流进给速度和磨料流速）的数学模型。对加工工件表面和表层的显微组织和冶金变化进行了深入分析，以揭示负责表面损伤消除和表面强化的机制。此外，还进行了四点弯曲疲劳试验以验证机械性能，与单次 AWJ 切削方法 (91 %) 和常规加工 (34 %) 被雇用。这证明了所提出的双加工AWJ加工方法对于提高单个机床平台上部件的功能性能是高效的。进行了四点弯曲疲劳试验以验证机械性能，与单一AWJ切削方法（91％）和常规加工（34％）相比，加工工件的疲劳寿命显着提高受雇。这证明了所提出的双加工AWJ加工方法对于提高单个机床平台上部件的功能性能是高效的。进行了四点弯曲疲劳试验以验证机械性能，与单一AWJ切削方法（91％）和常规加工（34％）相比，加工工件的疲劳寿命显着提高受雇。这证明了所提出的双加工AWJ加工方法对于提高单个机床平台上部件的功能性能是高效的。