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 (VB max ) to represent insert deterioration was measured. As would be expected, the general trend of how F increased as the number of milling pass (N pass ) increased agreed with the general trend of increasing VB max as N pass increased. But the F-VB max plot has shown a rather poor F-VB max relationship. This was the results of the different modes of tool deterioration affecting VB max differently, but VB max 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 VB max increased. Fracturing along the flank face of thin pieces effectively increased VB max 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/ ΔVB max , results from the effect of edge deterioration/ blunting on reducing the effective rake angle and thus increasing F is suggested and discussed.

Effects of Increasing Feed Rate on Tool Deterioration and Cutting Force during End Milling of 718Plus Superalloy Using Cemented Tungsten Carbide Tool

“…This value appears to be (or to be close to) the most commonly used value in nickel-based superalloy milling research [7,8,[13][14][15][16][17][18][19]. As has been explained [12], using f t of 0.05 mm/tooth, the edge radius of even the new tools is approximately the same as the un-cut chip thickness. An illustration of the radius (r1) comparable to the effective depth of the cut (d c0.05 ) is shown in Figure 1 (mid-schematic).…”

“…The same Ni-based alloy as used in our earlier studies [11,12] was used in the present study: Superalloy 718Plus. Its compositional specification is given in Table 1.…”

“…The gradual loss of edge material resulting in edge wear was also observable. The milling force (F) corresponds to each major mode of deterioration differently and thus the overall correlation of F-VBmax has been found to be poor [12]. The poor F-VBmax relationship has been attributed to the measurement of tool deterioration (wear) based on flank wear, as the measurement does not take into account the change of edge geometry.…”

“…Whether the variation of ft may affect the mode of tool failure has not been considered. The modes of tool deterioration [11] and how the progression of tool deterioration affects F [12], explained for end milling of a nickel-based superalloy, have been based on a ft value of 0.05 mm/tooth. This value appears to be (or to be close to) the most commonly used value in nickel-based superalloy milling research [7,8,[13][14][15][16][17][18][19].…”

“…Thus, in the present study, down-milling experiments using a nickel-based alloy and WC-Co tool have been conducted to aid in understanding how increasing f t may affect tool deterioration. A high f t value was used, and this value was twice as high as the commonly viewed low-medium f t value used in the previous study [12]. During either dry milling experiments or milling using a coolant, F was monitored.…”