Enhanced Cyclic Oxidation Resistance of a Single Crystal Superalloy with an Electrodeposited Reactive Element Oxide Coating
Cathodic electrodeposition was used to generate a rare earth (RE)-containing deposit on a single crystal Ni-based superalloy. The deposition parameters were optimised in order to get a RE oxy-hydroxide coating with a “well-fitted” dry-mud like morphology, i.e. presenting a multi-cracks network. A further thermal treatment was applied to dehydrate the deposit to obtain a well crystallised oxide coating (RExOy). The uncoated and RExOy-coated substrates were then submitted to cyclic oxidation tests at 1100°C in laboratory air. They demonstrated the efficiency of the coating as uncoated samples severely spalled after a few cycles whereas the coated ones did not lose their protective oxide layer even after 2000 cycles. This result was attributed to the formation of a duplex oxide scale very similar to that obtained on g/g’ coatings, to the presence of nanograins at the RExOy/scale interface and to the Hf-rich oxide pegs at the scale/substrate interface.
Toshio Maruyama, Masayuki Yoshiba, Kazuya Kurokawa, Yuuzou Kawahara and Nobuo Otsuka
F. Pedraza et al., "Enhanced Cyclic Oxidation Resistance of a Single Crystal Superalloy with an Electrodeposited Reactive Element Oxide Coating", Materials Science Forum, Vol. 696, pp. 278-283, 2011