Mustafa N. Jawhar; Muna K. Abbass; Israa A. Aziz; Fuad Khoshnaw
Abstract
The pack cementation process was used to create a type of Y2O3+ZrO2 doped Cr-Co-modified aluminide coating that takes advantage of the synergistic effects of nano Y2O3 and ZrO2 particles. ...
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The pack cementation process was used to create a type of Y2O3+ZrO2 doped Cr-Co-modified aluminide coating that takes advantage of the synergistic effects of nano Y2O3 and ZrO2 particles. A Ni-based superalloy (type IN625 type) was coated with pack powder containing: Al as a source of aluminum; Cr as a source of chromium, Co as a source of cobalt, NH4Cl as a source of activator; nano Y2O3-ZrO2 as a source of reactive element oxide; and Al2O3 as a source of filler metal. The process was carried out for 6 hours at 1100oC temperature. The microstructure characterization of the coating was performed by SEM, EDS, and XRD. It was found that the cross-section of the coating obtained was uniform and free from cracking. The maximum hardness value was found at the outer layer (997H.V.) and decreased toward the core sample core (366H.V.). The coating's microstructure consists of an outer layer, a transition layer, and an IDZ. The average coating thickness is 132.37, 36.11, and 37.65µm for the outer layer, transition layer, and IDZ, respectively. The XRD analysis of the coating system after 6 hours at 1100oC revealed phases formed by AlNi3, CoO, Al-Cr-Co, and Cr4NiZr. The n (growth rate time constant) and Kp (parabolic rate constant) values increase with increased oxidation temperature. It was found that adding Zr and Y to the Cr-Co-modified aluminide coating might increase the oxidation resistance.
