Morphological Characterization and Tribological Properties of TiCoNi Alloy Coatings on Ti–6Al–4V Alloy via Laser Deposition

Abstract

The goal of this work is to improve the Ti–6Al–4V alloy's hardness and tribological behavior. Coaxial laser surface cladding was used to develop intermetallic layers of nickel (Ni), cobalt (Co), and titanium (Ti). Laser power of 900 W, beam spot size of 3 mm, powder feed rate of 1.0 g/min, and gas flow rate of 1.2 L/min are the optimized parameters used for laser depositions. The laser scan speeds were adjusted between 0.6 and 1.2 m/min. Investigations were conducted into the effects of powder admixture and laser parameters on the fabricated coatings' microstructure, tribological behavior and hardness. X-ray diffractometry (XRD), energy dispersive spectroscopy (EDS) with Scanning electron microscopy (SEM) was employed for the characterization of the microstructural evolution and phase identification, respectively. Additionally, the tribological experiment was conducted via UMT-2 –CETR reciprocating tribometer, and the coatings’ micro-hardness characteristics were examined using EmcoTEST DURASCAN. The micrographs exhibit no signs of porousness, cracks, or stress introduction, according to the results. For every manufactured sample, good metallurgical adhesion was obtained. By comparing the hardness of the ternary coating (Co–Ni–10Ti deposited at a scan speed of 1.2 m/min, with a hardness of 980 HV) to the substrate (Ti–6Al–4V, with a hardness of 330 HV), a hardness increase of approximately 2.96 times was observed. Furthermore, the Co–Ni–10Ti coating, deposited at a scan speed of 1.2 m/min, demonstrated a 51.1% reduction in the coefficient of friction (COF) compared to the base alloy, indicating superior anti-wear performance. The enhanced properties are attributed to the formation of hard intermetallic compounds such as Ti–Co, Co2Ti, Al5Co2, and Ni3Ti, along with their uniform distribution and finely tuned grain sizes.