Effect of chromium content on the dry machining performance of magnetron sputtered CrxC coatings

Physical vapor deposition (PVD)-coated cutting tools are used extensively in global manufacturing for reducing production costs and improving productivity in the high-speed machining operations. In this paper, the tribological characteristics and machining performance of chromium carbide (CrxC)-coated cemented carbide tool inserts and micron-drills were assessed in dry machining. CrxC coatings have been deposited with different optical emission monitoring (OEM) set values of chromium target “poisoning” by closed field unbalanced magnetron (CFUBM) sputtering and OEM control. The microstructures and mechanical properties of CrxC coatings have been characterized by SEM, nanoindentation and adhesion techniques. The tribological properties of the coatings have been tested against different counterbodies under dry conditions using an oscillating friction and wear tester. Indexable inserts with CrxC coatings were applied to turning AISI 1045 steel and JIS C5191 phosphor bronze material by a lathe. Micron-drills with CrxC coatings were adopted in the ultra high speed (105 rpm) PCB through-hole drilling test. Experimental results indicate that the coating microstructure, mechanical properties and wear resistance vary according to the chromium content. Cr0.182C-coated inserts showed the best wear resistance in 1045 steel turning test. Cr0.688C-coated tools have excellent performance in both phosphor bronze turning and PCB through-hole drilling tests. The service life of Cr0.688C-coated tool is 15 times greater than that of an uncoated tool in PCB through-hole drilling test.