Progression of tool deterioration and related cutting force during milling of 718Plus superalloy using cemented tungsten carbide tools

Abstract

Understanding how tool deterioration affects total force (F) during milling of Ni-based superalloys is important for the improvement of machinability of the alloys and serves to clarify whether and how an F-based method for monitoring tool deterioration is possible. In this study, a series of milling experiments have been conducted on 718Plus Ni-based alloy using cemented tungsten carbide tool inserts. F was monitored, and the conventional flank wear (VBmax) to represent insert deterioration was measured. As would be expected, the general trend of how F increased as the number of milling pass (Npass) increased agreed with the general trend of increasing VBmax as Npass increased. But the F-VBmax plot has shown a rather poor F-VBmax relationship. This was the results of the different modes of tool deterioration affecting VBmax differently, but VBmax did not represent fully the true cutting edge of the deteriorating tool insert. Chipping and breakage of the inserts confined in the cutting edge area, resulting in the significant blunting of the edge, caused a high rate of F increase as VBmax increased. Fracturing along the flank face of thin pieces effectively increased VBmax without increasing the cutting edge area and without further blunting the edge, thus no increase in F was required. That the high rate, meaning high ΔF/ΔVBmax, results from the effect of edge deterioration/blunting on reducing the effective rake angle and thus increasing F is suggested and discussed.