Deposition of hard solid-lubricating composite coating on Ti-6Al-4V alloy with enhanced mechanical, corrosion, and electrical discharge wear properties

In the present work, a hard solid-lubricating clad layer has been developed on Ti-6Al-4V substrate by pre-placed powder TIG cladding technique to enhance the mechanical, corrosion and electrical discharge wear properties. The combining effect of Ti, Ni, and Si coating powders with different % of La2O3 in the N2 environment has been studied. The phase analysis detects peaks of both hard (NiTi, TiO2, and TiAlN) and solid lubricating (LaNi5 and Si3N4) phases. The sub-surface analysis shows defect-free cladding with good metallurgical bonds and refined microstructure near the interfacial zone. Mainly short and long dendrite, fish-bone-like, lamellar and short needle-like microstructures are observed. Two times higher microhardness in the range of 578.51 ± 13.99 HV0.5 (Sample S4) – 603.56 ± 9.66 HV0.5 (Sample S1) is observed. Mechanical wear analysis reveals a rigorous decrease in the coefficient of friction which is 14.5 times much better than titanium substrate. The prominent mechanism for mechanical wear is a combination of abrasion (Sample S1 and S2) with adhesion (Sample S3 and S4) with the lowest and highest wear rate of 63.92 ± 8.34 mm3 N−1 m−1 (Sample S4) and 154.52 ± 13.27 mm3 N−1 m−1 (Sample S1) respectively. The corrosion rate is found much lower than titanium substrate. The chance of the electrical discharge wear reduced to 81.90 % which is much better than titanium substrate. These results demonstrate that fabricated coating on Ti-6Al-4V substrate can be used in any of the mechanical, corrosion, and electrical discharge wear environments.