A study on the influence of thermally assisted novel hybrid methods on the drilling behavior of Ti6Al4V alloy

Abstract

The paper focuses on the drilling behavior of Ti6Al4V alloy under dry, MQL, hot (also expressed as heat-assisted machining), and hybrid (hot+MQL) environments. The surface roughness and morphologies, power consumption, drilling force, microhardness, and microstructural behavior using electron backscatter diffraction (EBSD) analysis were studied. As a result, the lowest roughness value was obtained in the MQL, followed by dry, hot and hybrid drilling environments. Based on SEM investigation on machined surfaces, the defects i.e., smearing, chip debris and side flow were found to be the main causes of poor surface quality, especially under hot and hybrid-assisted drilling environments. According to the Euler color distribution, the hot working affected the machined surface up to the bulk material with a length of 98 µm. The hot drilling process led to the recrystallization of the grain structure, and the distribution, sizes, and characteristics of the phases were affected by the temperatures. A partially recrystallized grain structure was observed in the IPF maps of the hybrid drilling environment at a distance of 10 µm from the machined surface. The crystal orientation of machined Ti6Al4V under hybrid-assisted environment was very similar to dry machined crystal orientation indicating stability in the microstructure.