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Surface integrity is an important factor affecting service performance of parts. Favorable machined surface state can greatly improve fatigue life of parts. Multi-process composite manufacturing is a common processing method in high-end manufacturing. In this study, the surface integrity and fatigue properties of nickel-based single-crystal superalloy DD6 after grinding-shot peening composite manufacturing were investigated. The influence of grinding and shot peening process parameters on the surface integrity of DD6 was introduced in detail and mainly analyzed the changes of surface topography and roughness, microstructure, microhardness, residual stress, fatigue life, and fracture morphology. The results show that compared with grinding, grinding-shot peening composite manufacturing increases the surface roughness with the increase of process strength. Grinding-shot peening composite processing will aggravate the shear fracture degree of γ phase and γ′ phase, forming a deeper surface plastic deformation layer; the surface microhardness reaches 645 HV; the hardened layer depth reaches 110 μm; and the residual compressive stress introduced on the surface improves with the increase of process strength. The fatigue life of composite manufacturing at 760 °C is 2.06 times longer than that of grinding. The fatigue fracture surface cracks along the {111} crystal plane. The grinding-shot peening composite manufacturing can slow down the crack propagation to the surface and prolong the fatigue life. [ABSTRACT FROM AUTHOR]

Aeroengine is the main power source of aircraft, and its operation stability and fatigue performance are directly related to flight safety. As a widely adaptable finishing process, vibration finishing can effectively reduce the surface roughness and improve the fatigue performance of the workpiece. At present, it has been widely used as the decoupling method before the last process or strengthening process of aeroengine blade parts manufacturing. In the traditional process, the surface should be polished by hand before vibration finishing. This paper studies a new process method of vibration finishing directly on the milled surface, which is of positive significance to reduce the instability of manual polishing quality and ensure the consistency of machining quality. Several groups of different milling surfaces are designed to form milling surfaces with different morphological characteristics. These surfaces are processed for a long time with the same vibration finishing process parameters. The research results show that when polishing the milled surface, the surface roughness will fluctuate with the extension of time, and its surface quality is not completely positively correlated with the processing time; By defining the eigenvalues on the roughness change curve, and establishing the mapping relationship between milling process parameters and initial surface roughness parameters and eigenvalues, this paper explores the method of controlling milling process to affect the surface quality of vibration finishing and establishes the relevant mapping model. On the basis of establishing the model, reverse optimization is carried out to select the milling surface roughness and machining parameters that are most conducive to the vibration finishing process. Finally, using SEM characterization technology, high-power microscopic characterization of the machined surface of vibration finishing and the surface of roll polishing grinding block is carried out to explore the mechanism of surface roughness fluctuation in the machining process. [ABSTRACT FROM AUTHOR]