Subsurface deformation after dry machining of grade 2 titanium

The effect of machining with and without lubricant on the depth of the affected deformation zone containing extensive twinning and the residual stresses produced in the Grade 2 unalloyed titanium have been examined. To determine the degree of surface deformation, the level of residual stress developed in subsurface layer during machining was determined using a standard X-ray Diffraction (XRD) technique. It was observed that the residual stress is reduced by using lubricant. When machining without lubricant at a surface speed of 48.3 m/min., the residual stress was measured to be -90 MPa, while it was -40 MPa after machining with lubricant. It was also observed that increasing surface speed without using lubricant results in a higher residual compressive stress in machined materials. Twin density was also found to be increasing with the surface speed and twin density was higher when machining without lubricant for a given surface speed.