Process-structure relationship in the directed energy deposition of cobalt-chromium alloy (Stellite 21) coatings
| Autor: | Ziyad M. Smoqi, Joshua Toddy, Prahalad K. Rao, Harold (Scott) Halliday, Jeffrey E. Shield |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
Cracking
Materials science Additive manufacturing 02 engineering and technology engineering.material 010402 general chemistry 01 natural sciences Indentation hardness Corrosion Coating Residual stress lcsh:TA401-492 General Materials Science Directed energy deposition Inconel Microstructure Stellite coating Mechanical Engineering Metallurgy 021001 nanoscience & nanotechnology 0104 chemical sciences Mechanics of Materials Microhardness Stellite engineering lcsh:Materials of engineering and construction. Mechanics of materials 0210 nano-technology |
| Zdroj: | Materials & Design, Vol 197, Iss, Pp 109229-(2021) |
| ISSN: | 0264-1275 |
| Popis: | In this work, we accomplished the crack-free directed energy deposition (DED) of a multi-layer Cobalt-Chromium alloy coating (Stellite 21) on Inconel 718 substrate. Stellite alloys are used as coating materials given their resistance to wear, corrosion, and high temperature. The main challenge in DED of Stellite coatings is the proclivity for crack formation during printing. The objective of this work is to characterize the effect of the input energy density and localized laser-based preheating on the characteristics of the deposited coating, namely, crack formation, microstructural evolution, dilution of the coating composition due to diffusion of iron and nickel from the substrate, and microhardness. It is observed that cracking is alleviated on preheating the substrate and depositing the coating at a moderate energy density (~200 J·mm−3). The main finding is that cracking of DED-processed Stellite 21 coating at higher levels of energy density is linked to the elemental segregation of chromium and molybdenum, which form hard and brittle phases in the inter-dendritic regions. Cracking in the inter-dendritic regions is caused by residual stresses resulting from the steep thermal gradients at higher input energy. Localized laser-based preheating and moderate energy density mitigate steep temperature gradients and thereby avoid thermally induced cracking of the Stellite coating along the inter-dendritic regions. |
| Databáze: | OpenAIRE |
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