Study of Grain Boundary Oxidation of High Alloyed Carbon Steels at Coiling Temperature

Abstract

The effect of coiling temperature on selective oxidation behaviour of binary and ternary iron-based model alloys containing different contents of Si or Mn were investigated by SEM and SIMS. The experiments were carried out with a temperature ranging from 450 °C to 700 °C, under N2-5%H2 gas flow with a Dew Point of -3.3°C, for different durations. SEM images of binary iron-based model alloys revealed a decrease of grain boundary oxidation depth with increasing Silicon or Manganese content. At 530°C and 600°C SIMS results showed no Silicon diffusion toward surface, contrary to the results analyzed for Fe-x%Mn. Tests results and Wagner's theory application (specific cases Fe-0.2%Si and Fe-0.5%Si) showed that grain boundary oxygen diffusion coefficient "Do GB " is almost 60 to 70 times faster than oxygen bulk diffusion coefficient. These results helped to broaden knowledge of single-element effects on grain boundary oxidation, in addition, will contribute of the future works in new steels with complex alloy compositions.

Internal Oxidation of a Fe–Cr Binary Alloy at 700–900 °C: The Role of Hydrogen and Water Vapor

“…Despite slight differences in Cr concentration (0.8 wt.% in [55]) and hydrogen pressure (25 mbar in [55]), the ratio between GB tail penetration and bulk IOZ width, X IG /X IOZ , found in [55] is 2.6 which is in excellent accord with the value 2.9 obtained in the present study. The X IG /X IOZ , ratio is expected to increase with decreasing temperature [56]. While these data independently confirm the enhanced intergranular attack in H 2 /H 2 O for diluted Fe-Cr alloys observed in the present study, the role of alloy chemistry, grain size and especially that of humidity remains obscure.…”

“…3a, 5a). GB tails or intergranular internal oxidation has been previously reported by Auinger et al [54,55] and Ronqueti et al [56] for diluted (0.2-1 wt.%) binary Fe-Cr, Fe-Al, Fe-Si and Fe-Mn alloys exposed in humidified Ar-H 2 or N 2 -H 2 gas mixtures below FeO formation at 600-700 °C. Intergranular tails were found in Fe-Cr and Fe-Si but not in Fe-Al and Fe-Mn [54,55], while the pattern became more complex in ternary model alloys.…”

Intergranular oxidation of Ni-base alloy 718 with a focus on additive manufacturing

“…The estimated activation energy for this reaction is close to 280 kJ/mol [11,12]. A recent study carried out on Fe-0.5 % Si, showed that the O diffusion coefficient along GBs, determined using Wagner's theory, could be 60-70 times higher than through the bulk [13]. In this latter study, the intergranular oxidation kinetics was supposed to be controlled only by the diffusion of O through the GBs.…”

Selective Oxide Deposition on Fe-Based Alloys in Dry High Temperature Environment – A Review

“…They also suggested that a larger compressive stress due to more Fe2SiO4 in steels with a higher Si content. This resulted in a deeper penetration layer [70,[85][86][87][88].…”