Abstract
In some cases chromium, necessary for the resistance to hot corrosion, unfortunately tends to lower the solidus temperature of alloys destined to high temperature applications. However a decrease of its content in the bulk can be allowed by a Cr-enrichment of the alloys sub-surfaces. To examine this possibility in the case of refractory TaC-strengthened iron-based alloys, three {Fe(bal.) – 10Cr – 0.2 or 0.4C – 3 or 6Ta} – alloys were elaborated by foundry in inert atmosphere and subjected to Cr deposit and inwards diffusion by a pack-cementation process. Bulk and subsurface microstructures examinations and concentrations profiles were performed after each step of elaboration of the future coated alloys as well as after a 50 hours / 1000°C oxidation test in air. A 500μm-deep carbide-free sub-surface with a chromium content twice the bulk one was obtained for the 0.2C-3Ta and 0.4C-6Ta alloys (less deep for the 0.4C-3Ta alloy) and allowed the alloys resisting high temperature oxidation.
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