Product Code: ICAL05_P531

Silicon Laser Alloying for Metal Dusting Environment
Authors:
Muhammad Ejaz, Corrosion and Protection Centre; Manchester UK
Presented at ICALEO 2005

Metal dusting is catastrophic carburization process, which causes metallic materials to disintegrate into particles of graphite, carbides and metal dust. This type of degradation typically takes place in the temperature range 450-800oC in gaseous atmospheres of high carbon activity. The resistance to metal dusting can be improved by increasing the amount of silicon in a metallic material. The silicon content of an alloy is typically kept below about 2%, because it adversely affects the mechanical properties of the material; however, higher concentrations of silicon can be alloyed into the surface layer or applied as a protective coating. In this work, silicon was introduced into the surface of Alloy 800H with a 1.5 kW high power diode laser. The behaviour of the laser-treated alloy was studied in a metal dusting environment consisting of 80% CO and 20% H2 at 650oC. The results suggest that silicon protects the alloy by modifying the surface layer of oxide. The laser treatment also changes the microstructure of the alloy, increasing the diffusion of chromium to the surface and favouring the formation of protective chromium oxide.