Fe-Cr-C hardfacing alloys for high-temperature applications

L.-E. Svensson, B. Gretoft, B. Ulander and H.K.D.H. Bhadeshia

Abstract

The microstructure and phase chemistry of a Fe-34Cr-4.5C wt% hardfacing alloy has been investigated using transmission electron microscopy and microanalytical techniques. The microstructure is found to consist of large primary M₇C₃ carbides in a eutectic mixture of austenite and more M₇C₃. The results indicate that the microstructure of the undiluted alloy becomes configurationally frozen at a temperature of about 1150^oC during deposition by the manual metal arc welding technique. This allows the metastable austenite phase to contain a large chromium concentration (16 to 17 wt %), thus imparting good corrosion and oxidation resistance. Experimental data on the partitioning of chromium, manganese and silicon between the carbide phases are discussed in the context of the high-temperature stability of the alloy.

The provided research examines the microstructural properties and chemical composition of a high-chromium iron-based hardfacing alloy created through manual metal arc welding. This material features hard chromium-rich carbides embedded within a tougher austenite matrix, a combination designed to resist wear and oxidation at temperatures reaching 1000°C. Using electron microscopy and X-ray analysis, researchers determined that the rapid cooling inherent in the welding process results in a metastable state effectively frozen from temperatures exceeding 1150°C. The studies conclude that the alloy maintains a high chromium content in its matrix, which is necessary for durability in demanding environments. While the as-deposited structure is stable at room temperature, it may eventually equilibrate and change its phase distribution if subjected to prolonged thermal energy. Overall, the findings suggest this specific iron-chromium-carbon system has practical utility for industrial applications requiring sustained protection against surface degradation.

Journal of Materials Science, 21 (1986) 1015-1019.

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