High-Temperature Oxidation Behavior of $214$Cr-1Mo Steel in Air–Part 2: Scale Growth, Metal Loss Kinetics, and Stress Enhancement Factors During Creep Testing

The oxide-scale growth and metal loss kinetics during oxidation in air of 2 1/4 Cr-1 Mo steel were studied at 600, 700, and 800°C for times up to 1000 h, with cylindrical specimens similar to creep test pieces. The scale thickness (x) was observed to exhibit a gradually decreasing growth rate with the exposure time (t) according to approximated parabolic behavior of type $x2=Koss˙t$ at the temperature levels of 700 and 800°C. The coefficient $Kos$ exhibited Arrhenius-type temperature dependence with an activation energy value of 212 kJ/mol. At 600°C, parabolic behavior was not verified, and the scale thickness growth follows better a relation of type $logx=A+Bs˙logt.$ The metal thickness (y) was observed to exhibit a gradually decreasing loss rate with the exposure time according to parabolic behavior of type $y2=Kmls˙t$ at the three temperature levels. The coefficient $Kml$ also exhibited Arrhenius-type dependence with an activation energy value of 215 kJ/mol. These two values of $Q$ are close do the value for diffusion of iron on the chromium-rich internal oxide layer formed in the material. Based on the equations of metal loss kinetics, the variation of the cross-sectional area of the specimens with time could be determined and plots of stress enhancement factors developed to assess the effect of oxidation on creep testing results.