| Fe-Al-Cr weld claddings are currently being considered as corrosion resistant coatings for boiler tubes in coal-fired power plants. These alloys rely on both aluminum and chromium additions for corrosion protection in simulated coal combustion environments. In previous research, the hydrogen cracking susceptibility of these alloys was shown to be a strong function of the Al and Cr content of the weld overlay. However, the effect of composition on the cracking susceptibility was ultimately shown to be an effect of the alloy additions on the presence of ordered structures and carbides in the overlays. This improvement in cracking resistance is attributed to the hydrogen trapping potential of the carbide phases.;The research conducted herein exploits the beneficial effect of carbides for reducing hydrogen-cracking susceptibility. Titanium carbide, a well known strong hydrogen trap site in steels, is formed in situ during weld metal solidification of Fe-Al-Cr-Ti-C based welds without the need for heat treatment. Well-established solute redistribution models were adapted in order to develop a model that permits control over the microstructural evolution of TiC in Fe-Al-Cr-based weld overlays. The presence of TiC in Fe-10Al-5Cr (wt%) based welds was shown not to adversely affect the corrosion resistance compared to TiC-free weld material. More importantly, the presence of TiC has been shown to extend the weldable composition range of Fe-Al-Cr based overlays. |
