Microstructure Analysis of Ti-6Al-4V Laser Cladding

Abstract

The microstructure and phase configuration of Ti-6Al-4V laser cladding were investigated in this study. The cladding microstructures were divided into the base metal of the substrate and heat-affected zone (HAZ), and the weld metal of the weld. However, depending on the location, the microstructure shapes were different, owing to heat transfer effects. The final solidification area of the weld metal had a fine structure because of the rapid cooling on contact with the air layer rather than at the center. HAZ also exhibited a relatively fine structure, owing to the rapid cooling of the substrate contact. All microstructure compositions consisted of a lamellar structure of a lean V-content α phase and a rich V-content β phase. The lamellar spacing in the HAZ was 0.5 μm, which was narrower than the 1.5 μm weld metal. However, the average hardness of the HAZ was lower than that of the 500 HV weld metal because of the low alloy content in the HAZ area, as it was welded on a pure Ti substrate. The alloy content of the weld metal welded using Ti-6Al-4V constituent electrodes was high; therefore, the estimated hardness value was high despite the coarse microstructure. In the weld area, cracks were formed in the HAZ because of the pores generated through the separation of oxides and weld residual stresses. The microstructure, phase configuration, and defects of Ti-6Al-4V laser cladding were identified, and the cladding is useful for the cladding process. Key words: Ti-6Al-4V, Laser cladding, Heat affected zone, Lamellar structure, α and β, phase