Authors:
Jorge A. Ramos-Grez
Departamento de Ingenieri´a Meca´nica y Metalu´rgica, Pontificia Universidad Cato´lica de Chile, Vicun˜a Mackenna 4860, Santiago, Chile

David L. Bourell
University of Texas at Austin, Mechanical Engineering Department, Austin, Texas 78712

Madhav Rao Govindaraju
Karta Technologies, Inc., San Antonio, Texas 78249


 

A surface coating technique that uses a 1 kW CO₂ laser beam actuated by two high-speed raster-scanning mirrors was utilized to selectively consolidate predeposited powder coatings consisting of 50%Cr-50% Ni (wt %) over the surface of 347 austenitic stainless steel specimens. The oxidation resistance of the coated samples was evaluated by heating them in air at 750 °C for up to 300 h. The migration behavior of the coating elements was studied. Comprehensive characterization of the samples was performed using scanning electron microscopy, energy dispersive spectrochemical analysis, and optical metallography. Surface protective coatings produced by this technique demonstrated a strong metallurgical bond with homogeneous dilution, low porosity, and uniform thickness. Metallographical analysis showed migration of coating species toward the bulk preferentially by means of grain boundary diffusion as a result of high-temperature exposure. Preliminary results from this study demonstrate that the surface modification by high-speed selective raster-scanning of a high-power laser beam is a versatile and expedient technique that could be used for applications that require large surface area coverage for oxidation protection.