DTA-EGA determination of carbides chemically extracted from steel

Differential thermal analysis-effluent gas analysis (DTA-EGA) techniques have been applied to the determination of specific metal carbides in residues which are isolated from steels by chemical methods. In this method, a weighed portion of sample residue is transferred to the DTA sample-holder and subjected to programmed heating in a dynamic oxygen atmosphere. When combustion of the carbide occurs, a differential temperature response is recorded over a specific temperature range. The temperature range is used as an aid in identifying the specific carbide present. The thermal conductivity of the effluent gas is recorded and the signal resulting from the presence of carbon dioxide in the effluent gas is then used for the quantitative determination of the carbide. The DTA-EGA method has been applied to several experimental steels for determination of the carbides of zirconium, vanadium or titanium individually and for the determination of vanadium and zirconium carbides in mixtures of the two. Results for these metal carbides obtained by DTA-EGA agreed within 15% with those obtained by the lengthy chemical methods. The lower limits of detection, based on the original steel sample weight, were 0.02% for the vanadium and titanium carbides and 0.01% for zirconium carbide.