فهرست نشریات علمی دسترسی آزاد ایران

This study evaluates the dry drilling performance of three high-speed steel (HSS) drill types on AISI 4140 quenched and tempered steel: uncoated HSS-E, standard PVD (Std-PVD) AlTiN-coated HSS-E, and a novel supersonic free-jet PVD (SFJ-PVD) AlTiN-coated HSS-E developed by the authors. Performance was assessed via hole cross-section analysis, surface quality, cutting-edge wear, and chip morphology. The uncoated drill suffered severe thermal and mechanical degradation, including a thick white-etching layer (15–30 µm), extensive heat-affected zone (50–100 µm), microcracks, oxidation, and catastrophic edge chipping. The Std-PVD coated drill showed improved but still limited performance. In contrast, the SFJ-PVD coated drill delivered the best results: minimal subsurface damage (white-etching layer <3 µm, heat-affected zone 5–10 µm), lowest surface roughness (Ra ≈ 1.8 µm vs. 2.6 µm and 3.2 µm), minimal cutting-edge wear (~150 µm), and stable flank wear. It also produced continuous, easily evacuated chips, while others generated segmented/tangled chips. A weighted performance index (WPI) scored the SFJ-PVD, Std-PVD, and uncoated drills at 9.0, 6.2, and 3.8, respectively. The results indicate that the novel SFJ-PVD AlTiN coating developed for this study, significantly enhances dry drilling by improving wear resistance, reducing thermal damage, and stabilizing chip evacuation, highlighting its potential for sustainable dry machining of high-strength steels.