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.

This content is only available via PDF.
You do not currently have access to this content.