Friction and wear properties of rapid solidified H-Al-17Si alloys processed by UV assisted stir - squeeze casting with DLC-Star (CrN + a-c:H) coating under HFRR /

Abstract

Tribological properties of rapid solidified hyper eutectic AlSi17Cu3.5-4Mg0.6-0.8 (H-Al-17Si) alloy were investigated under different loading conditions. The alloy was produced by the rheo-stir squeeze casting process with the T-6 condition. Experimental studies were conducted using high frequency linear reciprocating rig (HFRR) with a ball-on-plate geometry. The effect of applied load (10-50 N) on the wear and friction (COF) coefficients were studied under dry, lubricated (SAE15W40), and coated dry (DLC-Star) sliding conditions. For dry and lubricated sliding, COF values of hyper eutectic AlSi17Cu3.5-4Mg0.6-0.8 alloy were 0.26 and 0.042. A lower COF value of 0.013 was recorded with DLC-star (CrN + a-c:H) coating under dry condition. Whereas, the least wear coefficient is also observed with DLC-star coating (4.6X10-5 mm3/N.m) compared to the dry and lubricated sliding conditions (2.7X10-3 mm3/N.m and 3.8X10-4 mm3/N.m). The developments in COF and wear coefficients were mainly attributed to the distribution and size of primary Si granules and the formation of transfer layers on the coated surfaces of AlSi17Cu3.5-4Mg0.6-0.8 alloy. Surface morphologies were examined using SEM, AFM, surface roughness profilometer, and advanced metallurgical microscope (AMM) analysis techniques.