Laser Cladding of MCrAlY Coatings on Stainless Steel

Abstract

MCrAlY alloys (where M stands for Ni,Co or both) are commonly used as overlay protective coatings in gas turbine engine components against high temperature oxidation and corrosion. The protective effect of these alloys is due to the formation of a continuous thermally stable oxide layer on the coating surface. In this work several types of MCrAlY alloys, differing in their elemental composition, have been deposited on austenitic stainless steel by means of laser cladding. The microstructure of the coatings have been characterized by SEM-EDS and XRD. As expected, elemental composition compatible with Ni/ ' Ni3Al, Ni/ -NiAl or γCo/β-(Co,Ni)Al phases are observed in hypoeutectic or hypereutectic microstructures depending on the alloy composition. The high temperature oxidation behavior of the coatings was evaluated by air furnace oxidation tests at 1100ºC for 200 h. The oxidized surface of the samples was examined by SEM-EDS and the oxides present identified by theoretical stoichiometric calculations. Results indicate the formation of a uniform Al 3 O 2 protective oxide scale with NiO, CoO, Y 2 O 3 /YAlO 3 and Cr 2 O 3 oxide inclusions.

High temperature oxidation behavior of laser cladding MCrAlY coatings on austenitic stainless steel

“…In a previous works [21,22], laser cladding parameters were studied in a NiCoCrAlYTa alloy to obtain an adequate aspect ratio, homogeneity, low dilution and a good metallurgical bond with the substrate. In this study, high velocity, a high powder feed rate and high laser power were combined to build overlapping coatings.…”

Tribology and high temperature friction wear behavior of MCrAlY laser cladding coatings on stainless steel

“…In previous work [18][19][20], laser cladding parameters were studied on a NiCoCrAlYTa alloy to obtain an adequate aspect ratio, homogeneity, low dilution and a good metallurgical bond with the substrate. In this study, high velocity, high powder feed rate and high laser power were combined to build overlapping coatings.…”

Microstructure and mechanical properties of NiCoCrAlYTa alloy processed by press and sintering route

“…The predominant phases were γ-Ni, attributed to the nickel matrix (cobalt-and chromium-rich solid solution), tantalum, and aluminum in solid solution and β-NiAl phase and nickel-, chrome-and aluminum-rich phases with cobalt and tantalum in solid solution. These phases have been identified via XRD by several authors [7,8,16,19]. The possible presence of tantalum carbide or other carbides was not detected by this technique due to their small size and volume fraction, as shown in Figs.…”