Effect of impurity addition on the corrosion and carburization behavior of alloy 800HT in CO2 environment at 600 °C
Muthu Shanmugam Mannan, Gokul Obulan Subramanian, Taejeong An, Changheui Jang
Abstract
The corrosion and carburization behavior of Alloy 800HT was investigated in CO 2 , CO 2 +CH 4 , CO 2 +CO, and CO 2 +O 2 environments at 600 °C (0.1 MPa) for 500 h. The addition of impurities resulted in reduction of oxidation but an increase in carbon activity. While O 2 impurity addition significantly reduced the oxidation rate and the carbon activity due to the high p(O 2 ). Transmission electron microscope and energy dispersive spectroscopy (TEM-EDS) results showed the development of thin Cr-rich and Mn/Cr spinel oxide layer and different shapes of Cr-rich M 23 C 6 carbides in the matrix region. The CO addition showed a larger carburization region in the matrix. In all conditions, a Cr-depleted region appeared beneath the chromia oxide layer. In addition, the impurities promoted the development of Cr-rich precipitates in the Cr-depleted region, which is not observed in pure CO 2 .