Thermal Gradient and Dilution Effects on the Microstructural Development of Laser-Cladded Titanium Alloy

Industries continuously develop laser-based advanced coatings to meet the required standards and performance levels of materials. Making tough, highly wear-resistant coatings that can shield the bulk substrate from surface deterioration is one method to achieve the desired qualities. Using surface modification techniques can be a practical way to get beyond these restrictions related to titanium and its alloy. With this study, we look at what happens to a grade 5 titanium alloy (Ti-6Al-4V) when a hybrid Ti-Cu-Al coating is applied using the laser metal deposition (LMD) process and different laser process parameters. Utilizing laser metal deposition, a Ti-Cu-Al layer was created on the Ti-6Al-4V alloy. The elemental and phase content of coatings, as well as their microstructure, were examined. Optical microscopy, scanning electron microscopy (SEM) with energy dispersive microscopy (EDS), and x-ray diffraction (XRD) were used to study Ti-6Al-4V/Ti-Cu-Al composites. The SEM images showed that the addition of Cu and Ti to Ti-Cu-Al coatings was spread out evenly. This was seen at 900 and 1000 W of laser power and 0.8 and 1.0 m/min scanning speeds. For certain samples, there was a strong metallurgical link with tiny pores and fissures between the coating and the substrate, whereas for other samples, there were none. The microstructure showed signs of grain refinement as the grains expanded in a dendritic and columnar pattern in the opposite direction of the heat flow. The coatings were also found to have an amorphous phase, as indicated by XRD analysis. Ultimately, it was found that the low dilution rate of 42.99% and fine dendritic microstructure were produced by the rapid cooling rate (at 1.0 m/min). Because the previously deposited layer had less energy density when the scanning speed was raised, the resulting longer but finer grains resulted in a decrease in layer thickness. The interaction of laser power, scanning speed, powder feed rate, and melt pool size affected the coatings' shape. At scanning rates of 1.0 and 0.8 m/min, Ti-6Cu-10Al had the least amount of dilution, at 42.99 and 50.90%, respectively.