Surface integrity and residual stress analysis of μEDM coated Ti-alloy miniature components

ABSTRACT

This work contributes to the surface topographical study of miniature Ti-alloy coated samples prepared by the micro-electrical discharge coating process using powder mixed dielectric medium. Two phases of experiments were conducted, first phase: using tungsten disulfide mixed in de-ionized water and second phase: using molybdenum disulfide powders mixed in deionized water. The produced micro-parts from both the phases of experiments were characterized for micro-hardness, indentation depths, wettability (in terms of the surface contact angle), residual stress, surface roughness, and surface crack density. The results indicated that MoS₂ coating is superior as compared to WS₂ coating obtained through the micro-EDM process for tribological applications where lubrication is necessary. The WS₂ coated samples have micro-hardness ranging from 705.8 HV to 880.34 HV, surface roughness from 0.604 microns to 0.660 microns, and a comparatively higher surface crack density and residual stresses are developed on the recast surface than the samples coated with MoS₂ powders. The samples coated with MoS₂ powders have a micro-hardness variation from 658.21 HV to 714.21 HV, surface roughness between 0.561 μm to 0.650 μm.

KEYWORDS:

• Surface
• topography
• residual
• stress
• micro-EDM
• crack
• wettability
• micro-hardness
• indentation
• modification
• roughness
• coating