Effect of the Platinum Electroplated Layer Thickness on the Coatings' Microstructure

CMSX 4 and Inconel 625 superalloys were coated by platinum layers (3 and 7 mu m thick) in the electroplating process. The heat treatment of platinum layers (at 1,050 degrees C for 2 h) was performed to increase platinum adherence to the superalloys substrate. The diffusion zone obtained on CMSX 4 superalloy (3 and 7 mu m platinum thick before heat treatment) consisted of two phases:gamma-Ni(Al, Cr) and (Al0.25Pt0.75)Ni-3. The diffusion zone obtained on Inconel 625 superalloy (3 mu m platinum thick before heat treatment) consisted of the alpha-Pt(Ni, Cr, Al) phase. Moreover,gamma-Ni(Cr, Al) phase was identified. The X-ray diffraction (XRD) results revealed the presence of platinum in the diffusion zone of the heat-treated coating (7 mu m platinum thick) on Inconel 625 superalloy. The surface roughness parameter Ra of heat-treated coatings increased with the increase of platinum layers thickness. This was due to the unequal mass flow of platinum and nickel.