Investigation of oxidation behavior and Thermal spray of mechanically milled CoNiCrAlY–YSZ powders
الموضوعات :
Mostafa Tahari
1
(Department of Materials Engineering, Isfahan University of Technology, Isfahan, Iran.)
Morteza Shamanian Esfahani
2
(Department of Materials Engineering, Isfahan University of Technology, Isfahan, Iran.)
Mehdi Salehi
3
(Department of Materials Engineering, Isfahan University of Technology, Isfahan, Iran.)
الکلمات المفتاحية: CoNiCrAlY, Oxidation behavior, YSZ, High velocity oxy-fuel,
ملخص المقالة :
In this study, the effects of mechanical milling and YSZ reinforcing on oxidation behavior of CoNiCrAlY coatings were investigated. Various amounts of YSZ particles (0%, 5%, 10% and 15 wt.%) were mixed with commercial CoNiCrAlY powder and milled for 24 hrs. Then, the mechanically milled and commercial powders were deposited on Inconel 617 substrate using High Velocity Oxygen-Fuel (HVOF) process. Freestanding bodies of nanostructured and conventional HVOF CoNiCrAlY coatings were oxidized at 1000 °C for different times to form the thermally grown oxide layer. X-ray diffraction analysis, scanning electron microscopy and X-ray mapping were used to analyze the scales formed on the surface of the oxidized samples. The results showed that nanostructured coatings exhibited higher porosity due to undesirable morphology of feedstock powders. This factor accelerated diffusion rate of oxygen into coating body. On the other hand, undesireable oxidation of nanostructured particles during spraying leads to increase in the oxidation rate of coatings.
S. Gong,“Microstructural evolution of CoCrAlY bond coat on Ni-based superalloy DZ 125 at 1050 °C”, Surf. Coat. Technol., Vol. 205, 2011, pp. 4374-4379.
pp.1600-1604.
pp. 8370-8379.
pp. 5253-5260.
V. Provenzano, J. M. Schoenung, “Effects of variations in coating materials and process conditions on the thermal cycle properties of NiCrAlY/YSZ thermal barrier coatings”, Mater. Sci. Eng. A, Vol. 425, 2006, pp. 94-101.
pp. 293-299.
U. Bardi, F. Borgioli,C. Borri, C. Giolli, A. Scrivani, “Isothermal oxidation resistance comparison between air plasma sprayed, vacuum plasma sprayed and high velocity oxygen fuel sprayed CoNiCrAlY bond coats”, Surf. Coat. Technol., Vol. 204, 2010,
PP. 2499-2506.
V. Provenzano, J. M. Schoenung, “Synthesis and Oxidation Behavior of NanocrystallineMCrAlY Bond Coatings”,J. Therm. Spray Technol., Vol. 14, 2005,
pp. 23-31.
pp. 227-233.
H. Herman,“Application of image analysis for characterization of porosity in thermal spray coatings and correlation with small angle neutron scattering”,Surf.Coat. Technol.,
Vol. 187, 2004, pp. 6-15.
“A study on the oxidation behavior of HVOF sprayed NiCrAlY–0.4 wt.% CeO2 coatings on superalloys at elevated temperature”,Mater. Chem. Phys., Vol. 119, 2010, pp. 449-459.
H. G. Chun, S. Y. Hwang,“A study on HVOF coatings of micron and nano WC–Co powders”, Surf. Coat. Technol., Vol.202, 2008,
pp. 5556-5564.
27. D. Toma, W. Brandl, U. Koster, “Studies on the transient stage of oxidation of VPS and HVOF sprayed MCrAlY coatings”, Surf. Coat. Technol., Vol. 121, 1999, pp. 8-20.