Advanced Materials & Processing

Biography

Biography: Jolanta Romanowska

Abstract

Hafnium or palladium modification of NiAl phase increases the oxidation resistance of aluminide coatings deposited on turbine blades in a hot section of jet engines. Small hafnium or palladium addition to aluminide coatings decreases the oxidation rate of turbine blades made of nickel superalloys. Small content of hafnium (0.1-1.0 % wt) improves high temperature mechanical properties of aluminized nickel based superalloys. Palladium modification increased the outer zone hardness. It is due to the presence of the σ and µ phases. The palladium or hafnium modified aluminide coatings have better oxidation resistance than the non- modified ones. The use of ‘co-doping’ has recently been emphasized as a strategy for optimizing the oxidation resistance of super alloys, conventional alloys and coatings. The comparison of structures of hafnium and palladium modified aluminide coatings deposited on pure nickel and CMSX 4 nickel superalloy is presented. Aluminide layers were deposited by the chemical vapor deposition (CVD) method. Hafnium was deposited simultaneously with aluminum. Aluminum was deposited from the AlCl₃ and hafnium from the HfCl₃ gas phases. Palladium was deposited by the electrodeposition method. The obtained coatings were examined using an optical microscope, a scanning electron microscope and an XRD phase analyzer. Both coatings consist of two layers; an outer, comprising the ß-NiAl phase and the interdiffusion one. The interdiffusion layer on pure nickel consists of the γ’-Ni₃Al phase, whereas on the CMSX4 – of the ß-NiAl phase. Small inclusions of Pd and Hf rich phases were found at the border of the layers on nickel, whereas inclusion containing Pd, Hf and refractory elements were observed in the interdiffusion zone on the CMSX4 superalloy.

The research has been supported by the National Science Centre, Poland Grant No. 2015/19/B/ST8/01645.

Recent Publications :

1. J. Romanowska (2014) Aluminium diffusion in aluminide coatings deposited by the CVD method on pure nickel. CALPHAD 44:114-118
2. J. Romanowska, M. Zagula-Yavorska (2013) Zirconium influence on microstructure of aluminide coatings deposited on nickel substrate by CVD method. Bulletin of Materials Science 36:1043-1048
3. J. Romanowska, J. Morgiel, .M. , J. Sieniawski (2015)  Nanoparticles in hafnium-doped aluminide coatings, Materials Letters, 145: 15 162-166
4. J. Romanowska, B. Wierzba, J. Markowski, M. Zagula-Yavorska, J. Sieniawski (2016) The Ni-Al-Hf multiphase diffusion, Arch. Metall. Mater. 587-592
5. M. Zagula-Yavorska, J. Morgiel, J. Romanowska, J. Sieniawski (2016), Microstructure and oxidation behaviour investigation of rhodium modified aluminide coating deposited on CMSX 4 superalloy. Journal of Microscopy, 261: 320–325.
6. P. Fima, J. Romanowska (2015) Activity of bismuth in liquid Ag-Bi-Ni alloys determined by equilibrium saturation method, Journal of Mining and Matallurgy, Section B: Metallurgy, 51:105-112