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

Elshaimaa Abdelnasser,Ahmed Nassef,Azza Barakat,Ahmed Elkaseer,Samar Elsanabary

doi:10.3390/ma13245677

Elshaimaa Abdelnasser, Ahmed Nassef + Show 3 more

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https://doi.org/10.3390/ma13245677

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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.

Highlights

Titanium-based alloys are attracting considerable attention in a wide range of industries due to their unique mechanical and physical properties [1]
In the case of conventional machining, the results showed a gradual decrease in cutting temperature with increasing cutting speed from 50 to about 100 m/min, the temperature increases with increasing cutting speed from about 100 to 150 m/min for all values of feed rate and depth of cut, see Figure 4a,d
In the case of conventional machining, the results show a decrease in surface roughness with increasing cutting speed for all values of feed rate and depth of cut, Figure 8a,d

Summary

Introduction

Titanium-based alloys are attracting considerable attention in a wide range of industries due to their unique mechanical and physical properties [1]. They have gained popularity in aircraft engine and airframe manufacture as they offer a strength to weight ratio higher than aluminum or steel, in addition to which they offer excellent corrosion and creep resistance [2,3]. The main factors for the low machinability of titanium alloys are their low thermal conductivity [8], high chemical reactivity [9], and low modulus of elasticity [10] all of which affect machining accuracy, damage to the cutting tool, surface finish and surface quality [1]

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