An investigation of surface damage in the high speed turning of Inconel 718 with use of whisker reinforced ceramic tools

The paper presents the results of an investigation of surface damage produced by whisker-reinforced ceramic cutting tools in the finish turning of Inconel 718. The effects of the cutting parameters, of the tool wear and of the coolant condition on damage to the machined surface was investigated experimentally. The surface generated by machining was examined by use of both a scanning electron microscope (SEM) and a high resolution scanning electron microscope (HRSEM). This showed the regions of the surface that were damaged to contain both geometric defects and changes in the metallurgical structure of the subsurface. The types and the extent of the surface damage were found to be dependent upon the cutting parameters, the size of the wear land and the coolant conditions. The extent and the character of the coarse-scale and the fine-scale damage were analyzed on 72 specimens for which the cutting speeds, feed rates and coolant conditions (wet and dry) and the degree of tool wear differed. The types of damage that occurred in the form of micro-cracking and breakage, plastic flow, cavities, side flow and built-up edges are discussed.