Performances of hybrid high-entropy high-Cr cast irons during sliding wear and air-jet solid-particle erosion

The so-called high-entropy alloys have attracted increasing interest. An originally defined high-entropy alloy contains more than five elements without an apparent host element, and each element has its concentration in the range of 5–35%. This concept challenges the conventional principle used in developing alloys. High-entropy alloys are usually nanostructured and show high strength, excellent resistance to high-temperature creep, and high resistances to wear. Using this concept, the authors previously modified high-Cr cast irons (HCCIs) by adding mixtures of various carbide-forming elements, and noticed that such tailored HCCIs possessed high sliding wear resistance but performed less impressively when impact force was involved. Based on these observations, we modified the high-entropy concept and tailored a commercial white cast iron as a base alloy, Fe–27Cr–2.5C–0.8Si, by alloying with a small amount of B, V, Nb, and W to form several new alloys or hybrid HCCIs. Hardness and toughness of the alloys were measured. Compared to the base alloy, these alloys showed much higher sliding wear resistances. However, air-jet solid-particle erosion tests showed that the performance of these modified alloys was similar to that of the base alloy during high-speed solid-particle erosion, indicating that high-entropy alloys possess significantly enhanced sliding wear resistance due to elevated hardness but may not be very effective in resisting erosion when impact force is involved, which is limited by their reduced toughness. The advantages and disadvantages of high-entropy alloys are generally discussed.