Research On High Surface Integrity Milling Process And Surface Creation Of GH4169 With Abrasive Waterjet

Nickel-based superalloy GH4169 has become an ideal material for hot end components such as aerospace engines due to its excellent high temperature performance.However,its poor machinability is a typical difficult-to-machine material.In view of the problems in the research of abrasive waterjet milling GH4169,such as the difficulty in controlling the milling depth and surface roughness,the lack of process optimization research,the need to improve the comprehensive evaluation index of surface integrity,and the unclear surface generation mechanism,this paper carried out the research on the process and surface generation of abrasive waterjet milling GH4169 with high surface integrity.Through the experimental study on the machining performance of abrasive waterjet milling nickel-based superalloy,the prediction models of milling depth and milling surface roughness are established.Through the analysis of variance,it can be seen that the selected five experimental factors have a great influence on the milling depth,and the abrasive flow rate has little effect on the milling surface roughness.The degree of influence on the milling depth from strong to weak is waterjet pressure,nozzle moving speed,track spacing,nozzle inclination angle and abrasive flow.The degree of influence on the surface roughness of the milling surface from strong to weak is the waterjet pressure,the nozzle moving speed,the nozzle inclination angle and the inter trace spacing.Through the optimization of process parameters in abrasive waterjet milling of nickelbased superalloys,the multi-objective evolutionary algorithm based on decomposition solves the multi-objective optimization problem with the largest milling depth and the smallest surface roughness.The genetic algorithm is used to solve the single-objective optimization problem with a fixed milling depth and the smallest surface roughness.The results of multi-objective optimization validation experiments show that the maximum relative errors of the milling depth model and the surface roughness model are 7.69% and 12.98%,respectively;The single objective optimization validation experiment results show that the maximum relative errors of the milling depth model and the surface roughness model are 13.64% and 10.35%,respectively.By studying the surface integrity of nickel based high-temperature alloys during abrasive water jet milling,a comparison was made between the improvement of abrasive particle embedding on the milling surface using pure water jet and small particle abrasive water jet.It was found that the surface improvement effect was better using small particle abrasive water jet.A single factor experiment was conducted to investigate the influence of process parameters on the proportion of Si elements on the milling surface and the embedding depth of abrasive particles.Two surface improvement schemes aimed at minimizing the proportion of Si element on the milling surface and minimizing the embedding depth of abrasive grains on the milling surface were obtained through orthogonal experiments.The differences in work hardening and residual stress between the two surface improvement schemes and the unimproved surface were compared.The results indicate that there is a significant hardening phenomenon on the surface obtained by using unimproved processing parameters,and the surface hardness obtained by the improvement plan with the goal of minimizing the embedding depth of abrasive particles is the lowest;Compared with the unmodified surface,the residual compressive stress on the surface obtained by both surface improvement schemes increased significantly,with the surface residual stress caused by the shallowest embedding depth of abrasive particles being the largest.Then,through fatigue experiments and analysis of fracture morphology,cracks induced by abrasive particle insertion were observed.Finally,a study was conducted on the surface generation of nickel based high-temperature alloys using abrasive water jet milling based on a finite element model.The fragmentation of spherical,cylindrical,frustum shaped,and decagonal prismatic abrasive particles at 90°,60 °,and 30°impact angles was analyzed in the finite element model of single abrasive particle impact GH4169.Study the influence of different impact angles on the machining profile and stress distribution in the finite element model of GH4169 single pass milling with multiple abrasive grains.The forming mechanism and stress distribution during the milling process were studied in the finite element model of GH4169 with multiple abrasive grains and multiple passes.Research has found that when the impact angle is 90°,the maximum machining depth and residual compressive stress are generated.