Temperature and silicon effects on tensile and corrosion behavior of chronium-molybdenum steel

Martensitic P91 grade steels containing 0.48, 0.96, 1.28 and 1.77 weight percent (wt%) silicon (Si) have been tested for evaluation of their tensile properties at temperatures ranging from ambient to 550°C. The effect of activation using accelerator-driven electron beams on the room-temperature tensile properties of steels containing 0.48 and 1.28 wt% Si has also been investigated. The results indicate that all four heats of steel exhibited dynamic strain ageing at temperatures up to 400°C. The activated specimens showed enhanced tensile strength but reduced ductility with increasing activation time, indicating radiation hardening of the tested materials. The electrochemically-polarized specimens showed more noble critical pitting potentials with increasing Si content due to the formation of more protective oxide films. While the tensile specimens tested at 550°C exhibited ductile failures, brittle failures were seen at ambient temperature. However, all activated specimens revealed cleavage facets, indicating predominantly brittle failures.