MICROSTRUCTURE, MECHANICAL AND OXIDATION BEHAVIOR OF NIOBIUM MODIFIED 9 CHROMIUM STEEL

摘要

Microstructure, mechanical and oxidation behavior of niobium modified 9Cr steel has been reported in this work. Cast microstructure consists of martensite along with retained austenite and undissolved carbide phases. Martensite and Carbide phase changes are observed with increasing temperature during high temperature x-ray diffraction. Tensile properties of the steel are dependent on hot working and subsequent heat treatment parameters. The best combination of strength and elongation is achieved for 80% hot rolling, followed by normalizing at 1100°C and tempering at 700°C. Creep curve consists of primary, secondary and tertiary regions. Cyclic oxidation curve follows near parabolic rate regime.