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Subsurface deformation and burr formation in nickel-based single-crystal superalloy under grinding

Liang Chunyou, Gong Yadong, Li Pengfei, Sun Jingyu, Jin Liya, Yin Guoqiang, Wen Xuelong, Bo Xin

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 2

art. no. e126, 2023

EN

Machined subsurface and burr of nickel-based single-crystal superalloys (SXs) were identified as a key factor to the aero-engine industrial requirements concerning high service performance and the precision of edge geometry, in particular the finishing operations as grinding. To clarify subsurface deformation behaviors and the mechanisms of burr formation when grinding SXs, first, the present investigation predicted slip stresses acting on slip systems in workpiece subsurface under grinding based on the theory of resolved shear stress in single crystal, and correlated theoretical possible slip traces with experimental observed slip band systems. Second, grinding experiments on nickel-based SXs with [00-1]/[010], [11-3]/[332], [-110]/[111] and [-1-1-1]/[-110] orientations were performed to determine the anisotropy deformational behaviors of workpiece subsurface. Lastly, the unreported free surface of burr was adopted to investigate the formation mechanisms for side burrs and exit burrs during grinding. Results show that subsurface deformation patterns present anisotropy and resolved shear stress contribute to slip in nickel-based SXs. High shear density layers/zones consisting of interacted slip bands are found in grinding-induced sub-surfaces. Slip induced plasticity is the dominant deformation mechanism in the formation process of side burrs and exit burrs in grinding of nickel-based SXs.

2

Evaluation of dimensional accuracy and surface integrity of cylindrical array microelectrodes and cylindrical array microholes machined by EDM

Sun Yao, Gong Yadong, Wen Xuelong, Xin Bo, Yin Guoqiang, Meng Fantao, Tang Benjia

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 1

art. no. e46, 2022

EN

In this study, the loss self-finishing method based on EDM reverse copy principle was proposed aiming to enhance the prepared efficiency of cylindrical array microholes. First, the effects of geometric parameters of microelectrodes on the diameter consistent error, inlet and outlet deviation, section profile, surface roughness parameters and the heat affected zone thickness were quantitatively investigated. The forming accuracy of cylindrical array microelectrodes obtained by self-finishing and multi-finishing methods were contrastively analyzed. Furthermore, 8 × 8 cylindrical array microelectrodes with diameter of about 185.18 μm and length of 2168.79 μm were fabricated by the loss self-finishing method for the first time. Besides, the size accuracy, surface morphology and surface roughness parameters of cylindrical array microholes machined using array microelectrodes prepared by loss self-finishing method were evaluated. Experimental results disclosed that the average consistent errors of inlet and outlet diameter for cylindrical array microholes, respectively, were 1.495 μm and 3.13 μm, indicating that the cylindrical array microelectrodes obtained by loss self-finishing method are capable to manufacture cylindrical array microholes with good surface quality and high dimensional accuracy.

3

Effect of grinding conditions on the friction and wear performance of Ni based singlecrystal superalloy

Xu Yunchao, Gong Yadong, Zhang Weiqiang, Wen Xuelong, Xin Bo, Zhang Huan

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 2

art. no. e102, 1--16

EN

In this work, four types of surfaces were prepared as follows: untreated one, dry grinding (DG), wet grinding (WG) and minimum quantity lubrication grinding (MQLG) for Ni-based single crystal superalloy. The effects of grinding conditions on the surface roughness and microstructure evolution were studied. Dry sliding tests of ground surfaces were carried out at room temperature. Through the quantitative characterization of the wear rate, the area, width and depth of the worn profiles, the friction and wear mechanism of superalloy prepared by different grinding conditions were analyzed. The results show that the MQLG surface with low surface roughness and work hardening behavior has the best wear resistance. The element transfer behavior from the GCr15 ball to the worn surface was detected by EDS analysis. The wear type is mainly abrasive wear, accompanied by slight adhesive wear and oxidation wear. It is shown that high-quality surface with nanocrystalline and high density dislocation structure produced by MQLG improves the tribological properties of superalloy, which provide theoretical guidance for the surface machining of single crystal blade to reduce fretting wear.

4

Experimental study of Ni-based single-crystal superalloy: Microstructure evolution and work hardening of ground subsurface

Xu Yunchao, Gong Yadong, Wang Zhongxu, Wen Xuelong, Yin Guoqiang, Zhang Huan, Qi Yang

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 2

74--84

EN

In the present study, the grinding experiment of second-generation nickel-based single-crystal superalloy DD5 was carried out under different grinding parameters. The grinding force was recorded during the grinding process, and it was found that it decreased with increasing grinding speed and increased with feed speed. The microstructure evolution of ground subsurface was obtained by optical microscope (OM) and scanning electron microscope (SEM), and the elemental distribution of γ/γ' phases was investigated by energy dispersion spectrum (EDS). The results show that there are two layers different from the bulk material beneath the ground surface: (i) a white layer (WL) with no obvious structural features under limited observation scale and (ii) a severe deformed layer (SDL) with the elongated and rotated γ' phase and the narrowed γ channel. Elements segregation behavior exists in both the white layer and severe deformed layer. The grinding parameters have a great influence on the thickness of the white layer, which is due to the elemental diffusion behavior caused by intensive thermo-mechanical load. There is work hardening in the white layer, and the hardening degree aggravates with the increase in cutting speed and feed speed.