Laser-clad Ni70Al20Cr7Hf3 alloys with extended solid solution of Hf: Part II. Oxidation behavior
Ni-Al-Cr-Hf coatings with an extended solid solution of Hf were fabricated by laser cladding a premixed powder with a Ni-Al-Cr-Hf ratio of 70∶20∶7∶3 onto a substrate of RENÉ 80. Isothermal oxidation tests in slowly flowing air reveal that the claddings have a lower weight-gain rate than the substrate itselt. Microchemistry and microstructures of the oxidized samples were examined using scanning electron microscopy (SEM) and Auger electron spectroscopy (AES). The improvement in oxidation resistance is believed to be at least partially due to the formation of large numbers of hafnium-rich oxide spikes penetrating the unoxidized sample.