Experimental study on grinding surface properties of nickel-based single crystal superalloy DD5

Abstract

Nickel-based single crystal superalloy DD5, a typical difficult-to-machine material, is an important material for blades of aero-engine and gas turbine. The major characteristic of single crystal material from polycrystalline material is that the single crystal material shows significant anisotropy within the material. In order to investigate the grinding surface properties of DD5 material, some basic experiments have been conducted. The shear modulus G(001) and elastic modulus E(001) in the (001) crystal plane of nickel-based single crystal superalloy along different crystal orientations were deduced firstly in this paper. The shear modulus G(001) and elastic modulus E(001) along different crystal orientations in the (001) crystal plane of nickel-based single crystal superalloy change periodically with the cycle of π/2. The DD5 grinding anisotropy experiment and grinding surface quality orthogonal experiment were conducted then. When the angle θ is 45°, the grinding surface roughness Ra is the minimum, obtaining the best surface quality. In the grinding process of nickel-based single crystal superalloy DD5, the influence order of each process parameter on surface roughness Ra is as the following: grinding wheel linear speed > feed rate > grinding depth. The optimal process parameters of the nickel-based single crystal superalloy DD5 plane grinding selected by the range and variance method are the grinding wheel linear speed is 30 m/s, the grinding depth is 20 μm, and the feed rate is 0.4 m/min. The grinding subsurface microstructure and debris surface morphology were observed finally. Under the process parameters above, a plastic deformation layer of about 2 μm appears on the grinding subsurface, and the γ phase and γ' phase in the plastic deformation layer twist seriously. A work hardening layer of about 0.5 μm appears between the grinding surface and the plastic deformation layer. The free surface of the debris is discontinuous, showing a serrated feature of a section.