Micro-electrical discharge coating of Titanium alloy using WS₂ and Brass P/M electrode

Abstract

The paper brings forward a novel technique for localized solid lubrication coating in intricate structures. Green compact powder metallurgy electrodes (P/M) (diameter: 1 mm to 1.25 mm) were prepared from mixture of WS2 and brass powder at various mixing ratios. The prepared electrodes were used for the deposition process in micro-EDM. A permanent metal mold was fabricated to prepare the micro-EDM P/M tools. The coating operation was performed at different parameter combinations and the coated samples were characterized for evaluation of metallurgical and tribological properties. Maximum metal deposition rate (MDR) of 0.312 mg/min was obtained at powder mixing ratio of 50:50, machining voltage of 80 V, and 50 % duty factor. Uniform surface was observed at powder mixing ratio of 70:30 (WS2: Brass). Maximum micro-hardness of 578.55 HV was observed for coated surface whereas the same for base material was 280 HV. XRD analysis confirmed the presence of WS2, Al2O3 in the coating. Lower wear rate of coated surface was found as compared to uncoated work piece, and a reduction in friction coefficient 0.4 (uncoated work piece) to 0.07 (coated work piece) was obtained.