Abstract
In addition to possessing an attractive combination of mechanical properties for turbine applications, certain modified 12-chromium alloys were found to be structurally stable after long-time static aging and service exposure at high temperatures. However, two precipitation reactions have been observed to occur unpredictably in 12 Cr-Co-W-V alloy. The precipitating phases have been identified, and their effects upon mechanical properties are reported. After about 200 hr at 800 to 950 F (445 to 510 C), precipitation of chromium-rich ferrite causes decreased impact resistance and increased hardness; after about 6000 hr under stress at 950 to 1200 F (510 to 650 C), sigma formation causes an extreme decrease in impact resistance and no significant increase in hardness.
