Effect of Predeformation on the High-Temperature Oxidation Behavior of 436 Stainless Steel

The effect of a 30% predeformation treatment on the high-temperature oxidation behavior of 436 stainless steel is investigated by oxidizing it at 900 degrees C for 100 h in air. After 48 h of oxidation, the undeformed sample primarily exhibits bilayer structures consisting of Cr-rich oxide and outer Fe oxide, while the predeformed sample predominantly displays a single-layer structure composed of Cr oxide. The oxidation mechanisms of predeformed and undeformed samples are clarified from the point of recrystallization through oxidation kinetic curves, surface and section micrographs, X-ray diffraction (XRD), electron probe microanalyzer (EPMA), scanning electron microscope (SEM), energy-dispersive spectroscopy (EDS), electron backscattered diffraction (EBSD), and line scanning characterization methods. The results show that after 1 h of oxidation, the grain size of the undeformed sample is 34.6 mu m, and the grain size of the predeformed sample is 16.0 mu m. This reduces the critical content required for the generation of protective Cr oxides and provides more diffusion channels for Cr elements, resulting in the formation of a greater amount of Cr oxides. Cr oxides can inhibit the formation of Fe and Mn oxides, thus delaying the onset of breakaway oxidation and improving its resistance to oxidation. Predeformation can refine grains size and produce a continuous dense Cr-rich oxide layer at the initial stage of oxidation. Compared with the undeformed sample, the predeformed sample can significantly delay the appearance of the time point in the breakaway oxidation process, thus improving the oxidation resistance of stainless steel.image (c) 2023 WILEY-VCH GmbH