Furação da liga de alumínio Al-Mg-Si 6351 T6 utilizando brocas helicoidais de aço-rápido revestidas com Diamond-Like Carbon

Abstract

Dry machining of aluminum alloys is a technique that has been widely addressed, especially in studies focused on contextualizing drilling within the "Green Manufacturing" concept. One of the challenges faced in this technique is the adhesion mechanism, which intensifies during the machining of aluminum alloys and the inherent complexities of drilling. In addition, given the use of high-speed steel—a material with significant representation in the total production of cutting tools—it becomes vital to investigate ways to improve its performance during machining. In this context, the family of diamond-like carbon (DLC) coatings presents characteristics that can be advantageous for dry machining, although some inconsistencies in application are still observed, thus encouraging the development of new research. Based on this, the investigation of the effects of feed rate, cutting speed, cutting wedge geometry, and DLC coatings during dry drilling of Al-Mg-Si 6351 T6 alloy was proposed, using AISI M35 high-speed steel twist drills, while evaluating chip formation, predominant wear mechanisms, machining forces, form and dimensional deviations, and surface texture. The methodology consisted of stages of material acquisition, preparation and characterization, experimental design, and description of response variables. A total of 108 unit tests were performed. Results confirmed the chemical, structural, and mechanical characteristics of the machined alloy and the material used to manufacture the cutting tools. Similar layers of hydrogenated amorphous carbon were identified in both coatings, classified as predominantly solid lubricants with sp2 hybridization and satisfactory adhesion to the substrate. In machining tests, it was found that minimizing the feed rate and maximizing the cutting speed provided better results. Improvements in dry machining were observed through the use of coatings, particularly the one composed of a chromium nitride layer. With the use of chip breakers, a slight improvement in the surface texture of the holes was noted, which, however, was offset by a significant and unexpected alteration in chip morphology. Future studies are needed to refine this cutting wedge geometry.