Interface Evaluation of MCrAlY Powder Bond Coat on 316 SS Processed with Laser Irradiation

Abstract

As aircraft and thermoelectric turbine blades work in aggressive environments (high temperatures and pressures), they are exposed to oxidation reactions. Ceramic coatings are employed to increase the turbine work temperature (improving its performance) and a bond coat (BC), base of particulate material of Ni-Cr-Al powders, which assure a good adhesion, gradual decrease in thermal expansion coefficient between the metallic substrate and the ceramic top coat, avoiding the oxidation effect in the metallic substrate. This research aims the study and comparison of two different deposition process routes of particulate materials of BC (MCrAlY) on AISI 316 stainless steel substrate. In the first case, the BC powder was pre-deposited by segregation method and irradiated by a CO2laser beam. In the second case, laser surface texturing was done on the stainless steel surface by a Yb: fiber laser beam, the BC was deposited by the same method, and further, irradiated by a CO2laser beam. The main focus of this work was to evaluate the resulting interface for both mentioned cases. For this propose, characterizations were made using the techniques of optical microscopy and roughness measurements. In the first case, homogenous layers of bond coat were obtained. Optical microscopy suggest the formation of a metallurgic bonding between the substrate and the MCrAlY. For the laser surface texturing, the surface roughness can be adjusted by the laser beam parameters.

Parameters Evaluation of Bond-Coat Deposited by CO₂ Laser Beam for Aeronautical Turbine Blades

“…Previews work of Teleginski et. al [9] examined by SEM coatings obtained by laser deposition, and indicated that during the laser treatment of a pre-deposited layer a small portion of the substrate material is also melted, mixing its elements with the coating composition. This mixing results in increased compatibility between the NiCrAlY coating and the substrate, leading to a metallurgical bonding.…”

Caracterização microestrutural da camada de NiCrAlY sobre Ti-6Al-4V processado por laser de Yb:fibra

“…A partir deste resultado da variação da distribuição granulométrica foi possível realizar testes para a sedimentação do pó de NiCrAlY. O procedimento de sedimentação em meio líquido tem gerado resultados promissores de deposição de camadas TBC [17,18] por ser um meio simples e barato em relação ao processo de jateamento de pó juntamente ao laser, visto que o equipamento para acoplar e distribuir o pó tem um valor mais elevado de investimento e pode aumentar os períodos de manutenção pelo entupimento do canal de saída do pó pela larga distribuição de partículas.…”

Single-step laser sintering of YSZ powder-beds to TBC applications

“…The AISI 316 L chemical composition is described in Table I. The methodology employed in the LSP of NiCrAlY was previously described elsewhere [10]. The YSZ (ZrO 2 with 8% Y 2 O 3 ) powder (Praxair) was milled in a nylon jar, using 25 g of YSZ balls with a diameter of 1.0±0.1 mm, until it reached particle sizes smaller than 12 μm (1190L, Cilas).…”