Preparation of amorphous palladium-base surface alloys on conventional crystalline metals by laser treatment

Abstract

An attempt to solve the problem of the high electrical resistance, based on the limited thickness of melt-spun alloys which restricts the utilization of the superior electrode characteristics of amorphous palladium based alloys, was made by laser processing to prepare an electrocalalytically active amorphous alloy covering a conventional crystalline bulk metal which would act as an electrical conductor. Laser surface melting and subsequent self quenching by an overlapping traverse with a continuous CO 2 laser beam at 500 W vitrified the entire surface of a Pd-25Rh-10P-9Si cast alloy in spite of reheating and remelting in part of the previously vitrified phase during the laser processing. Vitrification of a surface alloy of several tens of micrometer thickness on a substrate bulk metal by the laser process required that the surface alloy be bonded to the substrate metal prior to the laser processing in order to ensure rapid heat absorption from the surface alloy melt by the substrate metal during laser processing. The laser treatment of the crystalline Pd-25Rh-10P-9Si surface alloy bonded to nickel or nickel-plated metal substrates resulted in the formation of the amorphous surface alloy. However, if the heat treatment for binding the crystalline surface alloy to the substrate metal before laser treatment led to the formation of a heterogeneous surface alloy, it was difficult to vitrify the surface alloy.