Materials Science Forum, Vol.369-3, 695-702, 2001
An exploratory evaluation of the elaboration and protection properties of chromium- or aluminum-containing laser-surfaced coatings on titanium
In order to protect titanium against high temperature oxidation, coatings were prepared by laser alloying with Cr3C2 or Al4C3 powders predeposited on the metal. These coatings (150 mum thick with Cr3C2- and 70 mum. thick with Al4C3-incorporation) were two-phase with TiC precipitates in a matrix of alpha -Ti(Cr) or alpha -Ti(Al) solid solutions. These surface alloys were shown to be protective against isothermal oxidation only for temperatures near 900 degreesC for which the oxidized scales formed in oxygen in 48 hours did not lead to the breakaway phenomenon. This positive effect could be connected with the growth of an external TiO2 subscale due to outward cationic diffusion enhanced by the presence of Cr2O3 or Al2O3 mixed with TiO2 in the inner subscale.