High temperature oxidation of NiCrAlY coated Alloy 625 manufactured by selective laser melting

Abstract

The high temperature oxidation of fully SLM-processed NiCrAlY coated Alloy 625 parts was investigated between 800°C and 1000°C. For comparison, bulk NiCrAlY and bulk Alloy 625 were also fabricated using SLM. Two thin layers of NiCrAlY powder were lasered at the surface of Alloy 625 to form the bi-materials. Bulk NiCrAlY and bi-materials showed an improved oxidation behavior compared to Alloy 625. The oxidation of the NiCrAlY coating results in regions with a dense and continuous external Al 2 O 3 layer and regions composed of a mixture of external Cr 2 O 3 and internal Al 2 O 3 . Large EDS maps at the surface and cross-sections of the bi-material highlighted a heterogeneous distribution of constitutive elements of the NiCrAlY coating, resulting in some regions with an Al activity lower than the one required for the formation of a continuous and dense Al 2 O 3 layer (≤10 atomic percent). Low Al activity and high Al activity regions were related to the topography of the SLMed surface and correspond to hill and valley regions, respectively. In addition, cracks, mainly occurring in high Al activity regions, were observed across NiCrAlY specimens. The fabrication of coated but small components with a brittle coating by SLM is not trivial and needs further investigations.

NaCl-induced hot corrosion behaviors of NiSiAlY coatings

“…Among all the protective coatings, traditional NiCrAlY coatings are widely used due to their excellent oxidation resistance Ren et al, 2005;Li et al, 2010;Peng et al, 2013). Generally, the Cr and Al in this coating form dense Cr 2 O 3 and Al 2 O 3 at a high temperature to protect the inner parts from severe corrosion (Saharkhiz et al, 2020;Texier et al, 2020). In addition, Cr element inside the coating can promote the formation of Al 2 O 3 .…”