Preparation, microstructure evolution and performance of laser-cladded titanium alloy coating on mild steel

Abstract

Almost all types of steels are vulnerable when serving long-termly in a corrosive marine environment. Coating steels with titanium alloys is an effective way to improve the anti-corrosion performance. Herein, high-performance titanium alloy coatings were successfully prepared from Ti6Al4V powder via a laser cladding technology. The key technological and structural factors were systematically studied and discussed. The correlation between interdiffusion behavior and microstructure characteristics of the coatings was established. It is demonstrated that the well-controlled heat input and thermal diffusion can ensure the high performance. Powder feed rate showed an important influence on thermal diffusion, and it was found that a critical coating thickness of about 200 μm highly affected the coating structure and performance. A thin coating prepared at a low powder feed rate of 1.6 g/min was mainly composed of Fe-rich intermetallic compounds (Fe 2 Ti), leading to a defective and brittle structure, and poor corrosion resistance in 3.5% NaCl solution. While thicker coatings prepared at higher powder feed rates (3.2–6.4 g/min) mainly consisted of Ti-rich phases (Ti 0.8 Fe 0.2 and Ti 2 Fe), so they possessed higher bonding strength and better corrosion resistance. Finally, the optimum cladding powder of 1000 W and powder feed rate of 4.8 g/min for the formation of high-performance titanium alloy coating are given in the present work. It exhibited the lowest corrosion current density of 1.1×10 -7 A/cm 2 , and its wear loss was about one-seventh of that of a Ti6Al4V block in wear test owing to the high hardness above 600 HV 0.1 . The present high-performance titanium alloy coating prepared via a low-cost and short-flow laser cladding technology is promising for applications in marine engineering.