New Chemical Surface Treatments for Processing Titanium

This paper examines methods of removing lubricant residues (C, MoS₂), oxides (TiO₂) and ceramic coatings (SiO₂) from heat treated or hot formed titanium sections. Work handling systems for high production cleaning and descaling depend upon consistent rapid removal of these contaminants.

Diffusion bonding techniques where complete removal of oxygen effected areas is necessary requires special consideration. Chemical milling selectively attacks surfaces that are not uniformly cleaned. The resulting cratered surface is unsatisfactory for additional operations. Conditioning and treatment cycles prior to effective gage removal are tabulated.

The final phase of surface treatment discussed is a liquid nitriding process performed at 1480°F (805°C). The treatment develops a 0.001-0.002 m (0.025-0.050 mm) wear resistant surface on titanium alloys. Treatment time is 2 hs, which effectively reduces gall and wear problems characteristic of titanium. The lower coefficient of friction developed in the treated surface is a decided advantage where mating titanium parts are subject to frictional wear.