Self-lubricating TiN/MoN and TiAlN/MoN nano-multilayer coatings for drilling of austenitic stainless steel

Abstract

Self-lubricating TiN/MoN and TiAlN/MoN nano-multilayer coatings were fabricated on the HSS drills by a closed field unbalanced magnetron sputtering system. The as-deposited TiN/MoN and TiAlN/MoN nano-multilayer coatings exhibit a face-centered cubic structure with (200) and (111) preferred orientation, respectively. The TiN/MoN coating possessed higher hardness of 31 GPa than that of TiAlN/MoN coating (21GPa). Both of the TiN/MoN and TiAlN/MoN coating exhibit low coefficient of friction with values of about 0.32. The cutting force and temperature of cutting edge of TiN/MoN and TiAlN/MoN coated drills were remarkably decreased compared to uncoated drills during the dry drilling test in austenitic stainless steel. The numbers of drilling holes of TiN/MoN and TiAlN/MoN coated drills were 4.2 and 2.4 times larger than that of uncoated HSS drills. The build-up edge was avoided on TiN/MoN and TiAlN/MoN coated drills which resulted in better surface quality of drilled holes compared to uncoated HSS drills.