Precision Hard Turning of Ti6Al4V Using Polycrystalline Diamond Inserts: Surface Quality, Cutting Temperature and Productivity in Conventional and High-Speed Machining

Abstract

This article presents the results of an experimental investigation into the machinability of Ti6Al4V alloy during hard turning, including both conventional and high-speed machining, using polycrystalline diamond (PCD) inserts. A central composite design of experiment procedure was followed to examine the effects of variable process parameters; feed rate, cutting speed and depth of cut (each at five levels) and their interaction effects on surface roughness and cutting temperature as process responses. The results revealed that cutting temperature increased with increasing cutting speed and decreasing feed rate in both conventional and high-speed machining. It was found that high-speed machining showed an average increase in cutting temperature of 65% compared with conventional machining. Nevertheless, high-speed machining showed better performance in terms of lower surface roughness despite using higher feed rates compared to conventional machining. High-speed machining of Ti6Al4V showed an improvement in surface roughness of 11% compared with conventional machining, with a 207% increase in metal removal rate (MRR) which offered the opportunity to increase productivity. Finally, an inverse relationship was verified between generated cutting temperature and surface roughness. This was attributed mainly to the high cutting temperature generated, softening, and decreasing strength of the material in the vicinity of the cutting zone which in turn enabled smoother machining and reduced surface roughness.

Fundamental Investigation into Tool Wear and Surface Quality in High-Speed Machining of Ti6Al4V Alloy

“…The results show that turning at high cutting speed of 200 m/min using carbide inserts found to give approximately the same ranges of obtainable surface roughness and flank wear when compared with conventional machining at low cutting speed of 80 m/min, as seen in [ 38 , 39 ]. This also agrees with the results reported in [ 15 ], which led the authors to suggest machining Ti6Al4V alloys with high-speed machining for its high throughput when compared with conventional machining.…”

“…The high-speed machining of titanium alloys has been investigated by numerous research teams. Abdelnasser et al [ 15 ] carried out a study comparing high-speed and conventional hard turning of the most widely used titanium alloy (Ti6Al4V) using polycrystalline diamond (PCD) inserts. The metal removal rate (MRR) was doubled, and there was smoother machining with a more than 10% reduction in surface roughness when using high-speed rather than conventional machining.…”

Parametric Study and Optimization of End-Milling Operation of AISI 1522H Steel Using Definitive Screening Design and Multi-Criteria Decision-Making Approach

“…An increase in cutting speed, feed rate, and depth of cut causes plastic deformation and thermal softening of material and therefore increases MRR [51]. The chip thickness under MQL conditions is relatively smaller than in dry conditions, attributed to a reduction in temperature and adhesion between the cutting tool and chip [52]. Moreover, MQL causes chip breaking easily and improves the MRR [1,52].…”

“…The chip thickness under MQL conditions is relatively smaller than in dry conditions, attributed to a reduction in temperature and adhesion between the cutting tool and chip [52]. Moreover, MQL causes chip breaking easily and improves the MRR [1,52]. Figure 10 shows an increase in material removal rate (MRR) with an increase in cutting speed, feed rate, depth of cut, width of cut, and cutting conditions.…”

“…The chip thickness under MQL conditions is relatively smaller than in dry conditions, attributed to a reduction in temperature and adhesion between the cutting tool and chip [52]. Moreover, MQL causes chip breaking easily and improves the MRR [1,52].…”