Comparative evaluation of burr formation in low-speed, high-speed and novel laser hybrid high-speed micromilling of Inconel 718

Inconel 718 is a precipitate hardened nickel-based superalloy that has been widely used in the aerospace, power generation and biomedical industries because of its good high temperature strength, corrosion resistance and low cycle fatigue life. However, micro-machining is a difficult process to perform due to its extremely high strength, work-hardening characteristics and abysmally low thermal conductivity that result in unwanted burrs at the micro-level. Systematic comparisons of the behavior of burrs in different domains of machining and especially incorporating hybrid strategies are still limited. To fill this gap, a comparative study of burr formation is pursued in three different micromachining domains: low speed, high speed and a new laser-hybrid high-speed. The experimental study was designed using a Taguchi L16 orthogonal array to investigate the influence of spindle speed, feed, and depth of cut with uncoated and coated tools. Statistical robustness was strengthened using ANOVA to identify the significant effect of each factor on burr growth. It was found that higher spindle speeds are critical for reducing burr formation, and integrating laser assistance demonstrated an even greater suppression. Cutting speed, tool coatings, and feed were reported as the predominant factors in low-speed, high-speed and laser-hybrid high-speed domains, respectively; while depth of cut was identified as a secondary factor in low- and high-speed conditions, with coatings for laser-hybrid machining. The nACo tool had good capability to minimize burrs at low speeds; the uncoated tool performed well for high-speed cutting; and TiAlN was effective in laser-hybrid conditions. The results also confirm the potential of high-speed micromilling, with advances in parameter selection and tool coatings, to achieve superior edge quality and precision.