Electrodeposition of Pt–Ir alloys on nickel-base single crystal superalloy TMS-75

Platinum–iridium alloy coatings from amidosulfuric acid solutions have successfully been electrodeposited on nickel-base single crystal superalloy TMS-75 by direct current method. The effects of electrolyte temperature, current density and mole concentration ratios of [Ir3+]/([PtCl62−]+[Ir3+]), on the deposition rate, composition and crystallographic structures of Pt–Ir alloy coatings are investigated. It is found that with increasing electrolyte temperature, deposition rate and Ir content increase, whereas the grain size of Pt–Ir alloy coatings decreases. Smooth and dense Pt–Ir alloy coatings can be obtained at 1 A/dm2 and 353 K. Pt–Ir alloy coatings with expected compositions can be readily fabricated by controlling the mole concentration ratios of [Ir3+]/([PtCl62−]+[Ir3+]) in the electrolyte. A detailed investigation of the structure and morphology of electrodeposited Pt–Ir alloy coatings is also presented. XRD analysis revealed that all the coated Pt–Ir alloys have a single phase with f.c.c structure, and the lattice parameters of the coatings decrease linearly with increasing Ir content, suggesting that the coated Pt–Ir alloy system follows the Vegardʹs law.