Effect of alloy grain size on the high-temperature oxidation behavior of the austenitic steel TP 347

Abstract

Generally, oxide scales formed on high Cr steels are multi-layered and the kinetics are strongly influenced by the alloy grain boundaries. In the present study, the oxidation behaviour of an austenite steel TP347 with different grain sizes was studied to identify the role of grain-boundaries in the oxidation process. Heat treatment in an inert gas atmosphere at 1050 °C was applied to modify the grain size of the steel TP347. The mass gain during subsequent oxidation was measured using a microbalance with a resolution of 10 -5 g. The scale morphology was examined using SEM in combination with energy-dispersive X-ray spectroscopy (EDS). Oxidation of TP347 with a grain size of 4 µm at 750 °C in air follows a parabolic rate law. For a larger grain size (65 µm), complex kinetics is observed with a fast initial oxidation followed by several different parabolic oxidation stages. SEM examinations indicated that the scale formed on specimens with smaller grain size was predominantly Cr 2 O 3 , with some FeCr 2 O 4 at localized sites. For specimens with larger grain size the main oxide is iron oxide. It can be concluded that protective Cr 2 O 3 formation is promoted by a high density of fast grain-boundary diffusion paths which is the case for fine-grained materials.

Effect of Fast Multiple Rotation Rolling on the Oxidation Resistance of Super304H Stainless Steel in High-Temperature Water Vapor

“…6, which ensured the stability growth of Cr-rich oxide scale. The result is consistent with the literature, that Trindade et al [25] have studied the effect of alloy grain size on the high-temperature oxidation behavior of the austenitic steel TP347 and concluded that protective Cr 2 O 3 formation is promoted by a high density of fast grain-boundary diffusion paths which is the case for fine-grained materials.…”

Cyclic Oxidation Behavior of IN 718 Superalloy in Air at High Temperatures

“…One way of modifying the oxidation behaviour of an alloy is through the use of a surface treatment such as polishing, electro-polishing, grinding, shot peening, sandblasting, machining or cold rolling. The effect of surface treatments on oxidation have been studied previously [14][15][16][17][18]. As a result of surface treatment, energy is stored in the surface region of a metal in the form of dislocations [19,20].…”

Microstructural Aspect of Long Term Service of the Austenitic TP347HFG Steel / Wpływ Długotrwałej Eksploatacji Na Mikrostrukturę Stali TP347HFG

“…The designed fine-grained microstructure of TP347HFG steel (grain size ≥ 8) ensures high resistance to oxidation and higher plasticity (expressed as the elongation growth in creep tests) with the creep resistance similar to that of coarse-grained steels [2]. Fine-grained microstructure of TP347HFG steel also has an influence on a slower decrease in impact strength during its long-term service [8,9]. Performed identifications of precipitates revealed two types of carbides in the microstructure: NbC carbides and M 23 C 6 carbides (Fig.…”