Effect of Chromium Content and Heat Treatment Conditions on the Structure of Wear-Resistant White Cast Irons
Аннотация
In this study analyzed, the effects of heat treatment on the structure of white cast iron with different chromium contents (28 wt.%Cr to 32 wt.%Cr). To observe changes in the structure and increase its wear resistance, the cast materials were heat treated. The heat treatment was carried out in the following order: (1) quenching: two samples of each material were kept in the temperature range of 1000℃ for 1 hour and cooled with oil (QT(o)) and forced air cooling (QT(f.a.c.)), (2) tempering at a temperature of 200℃ for 2 hours were kept and cooled under the influence of room temperature (QT(c.r.t)). In addition, in order to study the microstructure of the cast samples and compare their state after the heat treatment process, the samples obtained from each material were not subjected to treatment (AC). The microstructures of the materials were analyzed using scanning electron microscopy (SEM), and the dimensions of the structural constituents were further processed using the ImageJ software. The obtained results show that the microstructure of the samples obtained in the as-cast state mainly consists of primary carbides such as M7C3 and M23C6 and an austenitic matrix. As a result of heat treatment, the metal matrix transformed from austenite to martensite, retained austenite phases remained, and at the same time, secondary carbides were precipitated throughout the matrix. Among the analyzed materials, the best characteristics were demonstrated by the heat-treated and oil-cooled sample with a Cr content of 31%. The second sample with a Cr content of 28% showed the worst wear resistance in the as-cast condition.