Research On Surface Layer Characteristics And Corrosion Resistant Of Milling Nickel Base Superalloy

FGH97 is a new generation of high temperature nickel base powder metallurgy alloy developed by China. Materials for its excellent thermodynamic properties are widely used in the development of aerospace, shipping and other undertakings. This paper combined with the milling surface features of component, including surface topography, surface roughness, residual stress and other factors, launched the study of relationship between milling process parameters and corrosion resistance of workpiece.Through the milling of nickel base powder metallurgy superalloy FGH97 experiments, this paper analyzes the effect of cutting speed, feed per tooth, axial depth of cut on the surface roughness, surface residual stress and work hardening. The experiment shows that: when cutting speed in the range of 30-70m/min, surface roughness change stability. If the cutting speed is more than 70m/min, tool tipping led to the rapid increase of surface roughness; with the increase of cutting speed, the surface residual stress is also increased; the surface roughness increases with the increasing of feed per tooth; the axial cutting depth increases, the surface roughness and surface residual stress increases slowly.3D surface topography under different milling parameters is characterized by using amplitude parameters and Motif method. When the cutting speed is 50m/min, the amount of feed per tooth is 0.10mm/z, the axial depth of cut is 0.20 mm, the minimum amplitude parameter shows that the surface topography after milling is relatively flat, there is no major peaks and valleys. In order to facilitate the characterization, this paper defined the Motif area ratio, which is defined as the ratio of machined surface on satisfying the threshold Motif area and the machined surface area. When the cutting speed is 50m/min, the amount of feed per tooth is 0.10mm/z, the minimum Motif area ratio shows that the machined surface has good surface topography. Axial depth of cut has a great impact on the 3D topography. Along with the increase of axial cutting depth, the surface morphology is getting worse.Because of the superior corrosion resistance of FGH97, there found no large area of corrosion, so this paper introduces the average corrosion rate to evaluate the corrosion degree of the workpiece. The average corrosion rate of the workpiece varies with the changes of surface roughness and surface residual stress, when the surface roughness is large, average corrosion rate becomes faster; when the surface roughness is small, the average corrosion rate becomes slower, the larger the residual tensile stress, the faster the corrosion speed, on the contrary, the smaller the residual tensile stress, the slower the corrosion speed.