The effect of texture location on ceramic inserts wear when turning Inconel 718 under low- and high-pressure lubrication

Abstract

The low machinability of nickel-based superalloys has been a major concern for researchers over the last few decades, prompting the development of various approaches to enhance it. Within this context, the present study integrates the key concepts of insert texturing and high-pressure lubrication to improve the tool life when turning Inconel 718 using recently introduced inserts named Bidemics^TM. These inserts are composed of a matrix of alumina, providing high hardness, where clusters of tungsten carbide (WC) are dispersed to increase toughness and thermal conductivity. A novel texture was designed and obtained on the inserts’ rake and flank faces by means of a nanosecond laser machine. The texture design includes tapered channels for fluid retention and a grid that facilitates its distribution within the cutting zone. Four categories of round Bidemics^TM inserts were tested: plain (NT), rake textured (RT), flank textured (FT), and a combination of the latter ones (CT). In addition, two lubrication pressures (15 bar and 70 bar) were used.

SEM and EDS analyses were conducted to assess the wear mechanisms as a function of the texture location. The chip morphology and quality of the machined surface in terms of surface finish and hardness were also investigated. Results show that flank texturing is the most effective strategy for mitigating flank wear, reducing the average flank wear depth (VB_mean) of the FT and CT inserts by around 30% compared with the NT case, regardless of the lubricant pressure. Whereas texturing on the rake face primarily facilitates lubricant penetration and distribution in the cutting zone. In addition, the application of high-pressure lubrication promoted chip fragmentation, while the use of textured inserts successfully reduced the average surface roughness under all investigated conditions.