Bifilm defects in Ti-inoculated chromium white cast iron

Abstract

In recent years, white chromium cast iron has gained a well-settled position among wear-resistant materials. In recent times, chromium cast iron samples containing titanium have attracted attention. In cast iron samples, titanium combines with carbon and forms TiC particles, which may be form a crystallization underlay for eutectic M7C3 carbides and austenite. Accordingly, the inoculation process occurring in the crystallizing alloy should result in the proper, regular distribution of fine eutectic chromium carbides in the austenitic matrix. The presented research was conducted on 20% Cr hypoeutectic white cast iron with the addition of 0.5, 1, and 2% of Ti. Ti inoculation and the presence of TiC allowed for superior wear properties to be obtained. However, the conducted study revealed a significant decrease in the impact strength of examined alloys, especially for the cast iron samples with a high amount of Ti, in which the TiC compounds agglomerated. Titanium compounds accumulate in clusters and their distribution is irregular. Most of the TiC compounds were transported by the crystallization front into the center of the castings, where micropores were formed, meaning they were no longer effective crystallization underlays. In the authors' opinion, the agglomerate formation is strictly connected with the appearance of bifilm defects in the casting microstructure. The conducted research shows how an incorrect volume of an additive may have negative influences on the properties of the casting. This is a vital issue not only from a technological point of view, but also for economic reasons.