Comparison of surface integrity for dry and wet drilling of 49Fe-49Co-2V alloy

Working performances of the components made out of 49Fe-49Co-2V alloy are closely related to the surface integrity of the drilled holes, which are influenced remarkably by the cooling conditions. The present study focuses on the surface integrity differences between wet and dry drilled 49Fe-49Co-2V alloy holes. The drilled hole surface roughness and topographies, metallurgical and mechanical properties, and the exit characterizations were obtained using optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction microscopy (EBSD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and Vickers hardness techniques, etc. The effects of cooling conditions on the surface integrity were concluded and the influence mechanisms were analyzed based on the force and temperature differences in drilling process with different cooling conditions. It is found that the surface roughness and the thickness of refined-grain region of the dry drilled holes are larger than those of wet drilled holes; work hardening induced by wet drilling is more serious than dry drilling; chippings occurred in the exits of the wet drilled holes due to the material brittleness, which could be avoided by dry drilling. The surface integrity differences of wet and dry drilled holes are closely related to the force and temperature differences in drilling process with different cooling conditions.