Microstructure and Oxidation Resistance of an Aluminide Coating on the Nickel Based Superalloy Mar M247 Deposited by the CVD Aluminizing Process

• Published in: Archives of metallurgy and materials 2013-09, Vol.58 (3), p.697-701
• Main Authors: Zielinska, M, Zagula-Yavorska, M, Sieniawski, J, Filip, R
• Format: Article
• Language: English
• Subjects: Alloys; Aluminides; Aluminizing; Aluminum; Chemical activity; Chemical synthesis; Chemical vapor deposition; Coating; Diffusion coating; Diffusion layers; High temperature; Interdiffusion; Intermetallic compounds; Intermetallics; Investigations; Microstructure; Nickel base alloys; Optical microscopes; Oxidation; Oxidation resistance; Oxidation tests; Phase transitions; Prolongation; Scanning electron microscopy; Solid solutions; Substrates; Superalloys; Thermal cycling; Thickness; Vapor resistance
• ISSN: 1733-3490; 2300-1909
• DOI: 10.2478/amm-2013-0057

An investigation was conducted to synthesize βNiAl coating on the nickel based superalloy Mar M247 in a chemical vapor deposition process (CVD). The low activity process of aluminizing was carried out for 8 hours at the temperature 1050°C. Surface morphology and cross-section microstructure of the diffusion coating were studied and compared by using an optical microscope, a scanning electron microscope (SEM) equipped with energy dispersive spectroscopy and an X-ray diffractometer. It was found that aluminide coating with the thickness of 37 μm consisted of two layers: an outer one and the inner interdiffusion one. The outer layer consists of single phase βNiAl. The inner one, consisted of βNiAl phase and carbides: MC and M 23 C 6 types which were originally present in the substrate. Cyclic oxidation test was performed at 1000°C for 1000h in the air atmosphere. The aluminized samples exhibited a small mass increase and the α- Al 2 O 3 oxide formed during oxidation test had a good adherence to the coating. The decrease of aluminum content in the coating with the prolongation of the oxidation time and the phase transformation of βNiAl to γ’ Ni 3 Al and to γNi solid solution were observed. The samples without the coating showed a strong mass decrease in comparison to the coated samples.