Dense titanium coatings by modified HVOF spraying

Titanium has an excellent corrosion property in chloride containing environments such as seawater. A modified high velocity oxy-fuel (HVOF) spray process was developed by introducing a mixing chamber between the combustion chamber and the powder feed port. Nitrogen gas was fed into the mixing chamber to control the temperature of the combustion gas generated in the combustion chamber. By controlling the flow rate of nitrogen, various Ti coatings with different degrees of oxidation and porosities could be fabricated. The densest coating produced by this process with surface polishing treatment maintained excellent corrosion protection over a steel substrate in artificial seawater in a laboratory test over 1 month.