Synergistic toughening by a layered microstructure and texture of Si-enriched ferritic/martensitic(F/M) heat resistant steel

Abstract

In order to achieve favorable heat corrosion resistance, it is effective to add high Si contents to F/M heat resistant steel. Unfortunately, the high Si content results in a significant deterioration of impact toughness. Determining how to balance heat corrosion resistance and impact toughness has been a challenge. In this paper, we optimize austenite isothermal hot-rolling (AIHR) technique to the 10Cr1SiY F/M dual-phase heat resistant steel with 1% Si(wt.), to obtain layered microstructure with thread-like δ-ferrite. This decreases ductile-brittle transition temperature (DBTT) from 149 °C to 15 °C, and increases impact energy from 8 J to 107 J, compared to the quenched and tempered steel with the same chemical composition. According to the instrumented Charpy impact tests, higher impact energy derives from the absorbing energy during crack propagation, accounting for 94.9% of the total absorbing energy. The weak interfaces in the layered microstructure effectively deflect cracks, while the {110} slip plane induced by strong textures from multi-pass rolling promoted dislocation slip, thus rendering plastic deformation and weakening the crack tip stress; synergistic interaction is responsible for the improved toughness, resulting in the delamination fracture of the steel. The reduced grain size and M23C6 phases also contributes to the improved toughness.

Keywords

• Si-enriched F/M heat resistant steel
• Austenite isothermal hot-rolling
• Layered microstructure
• Texture