Initial oxidation behaviour of niobium stabilized TP347H austenitic stainless steel - Effect of grain size and temperature

Abstract

High temperature corrosion of austenitic TP347H steels with two grain sizes was studied at 600-750 8C in dry air. A relationship between oxidation rate and grain size was found. The surface oxides consisted of iron enriched (Fe,Cr) 2 O 3 nodules and a (Cr,Mn) 2 O 3 scale. Initial oxidation with both grain sizes followed cubic kinetics, a combination of fast oxide formation via oxide grain boundary diffusion at the beginning of oxidation and parabolic kinetics combined with oxygen dissolution to the steel through breakaway oxidation nodules. Above 650 8C, the breakaway oxidation became more severe in coarse grained steel and fine grained steel started to destroy the nodules. Better oxidation resistance was achieved with smaller grain size, especially at higher temperatures. Reducing the TP347H steel grain size lowers the critical chromium concentration needed for the formation and recovering of the protective oxide scale.

Effect of Ultrasonic Shot Peening on Oxidation Behavior of T91 and SS347 Steels in Air and Steam at 650 °C

“…The SS347 steel contains austenite grains, with twin bands in many of the grains. The mean intercept length of grains is generally 48-50 lm (Ref [13][14][15]. The average bulk hardness of the as-received SS347 specimen was measured to be 220 ± 5 VHN.…”

“…Detachment of oxide scale causing impact damage and downstream blockage resulting in overheating has proved to be a serious problem in super-heater tubes (Ref 12). Type SS347 is a high-carbon, columbium (niobium)-and tantalum-stabilized austenitic chromium-nickel stainless steel, found suitable for applications demanding hightemperature resistance against fall in mechanical properties and environmental degradation (Ref 2,13,14). SS347 steel shows good strength and oxidation resistance up to 680°C due to higher amount of Cr and Ni ( Ref 13).…”

Investigation on High Temperature Corrosion Characteristic of Super304H, TP347H, and HR3C Steel in an Ultra‐supercritical Coal‐fired Boiler▴

“…Therefore, only few kinds of materials can be applied in manufacturing final super‐heater and re‐heater of ultra‐super critical power plant unit. Nowadays, Super304H (18Cr9Ni3CuNbN), TP347H (1Cr19Ni11Nb), and HR3C (25Cr20NiNbN) are widely used [5–7]. Because super304H has a good performance of endurance strength and high‐temperature steam oxidation resistance [8].…”

Investigation on Oxidation Behavior of Super304H and HR3C Steel in High Temperature Steam from a 1000 MW Ultra-Supercritical Coal-Fired Boiler

“…Super304H has good endurance strength and high temperature steam oxidation resistance, HR3C has better heat intensity property. Super304H and HR3C have been widely used in the manufacture of superheater or reheater [10,11].…”