Int J Adv Manuf Technol (2013) 68:1573–1581

DOI 10.1007/s00170-013-4944-7

Damage of the machined surface and subsurface in orthogonal milling of FGH95 superalloy
Du Jin, Zhanqiang Liu*

Abstract:FGH95 is one kind of powdermetallurgy (PM) superalloy which has excellent mechanical properties at hightemperature. It has been developed for turbine disc applications to improveaeroengine efficiency under higher operating temperatures. However, this kindof superalloy is very difficult to machine because of its poor thermaldiffusivity and work-hardening properties during the machining process. Themachining process can lead to damage of the machined surface and subsurface.Thus, the purpose of this paper was to investigate damage of the machinedsurface and subsurface in hard machining of FGH95 PM superalloy. Orthogonal millingexperiments using coated carbide inserts were carried out on a CNC machiningcenter. The machined surface was observed and recorded using

an optical microscope, whitelight interferometer, and scanning electron microscope. Machined surfacedefects were recorded and analyzed. The effects of cutting speed on machinedsurface roughness, white layer thickness, plastic deformation, and microhardnesswere investigated. The research results show that better surface roughness canbe generated at higher cutting speeds, while several defects appeared on theFGH95 machined surface. White layer thickness and machined surface microhardnessincrease with the cutting speed. Also, plastic shear strain in the machinedsurface layer increases with cutting speed. The depth of plastic deformation decreaseswith the increase of cutting speed. These investigation results are essential forthe evaluation of PM superalloy surface integrity and are significant for theprediction of PM superalloy service life.

Keywords: Machining. Surface damage.FGH95. White layer. Plastic deformation