Nb and B Microalloying in Carburized Gear Steels: Enhancing Wear and Corrosion Resistance

The beneficial effects of Nb and B have been observed in some steel grades. Previous studies have shown that Nb microalloying can enhance the wear resistance of 100Cr6 bearing steel, owing to the hard precipitation of NbC [12-13]. Additionally, Nb microalloying can reduce stress corrosion cracking susceptibility by refining the grains and creating a uniform microstructure [14-15]. However, limited research has been conducted on the performance of carburized gear steels. In recent years, boride has been utilized in a new generation of wear-resistant and corrosion-resistant materials, such as high boron cast alloy, high boron white cast iron, Fe-B alloy, Fe-Cr-B alloy, or Fe-C-B alloy, among others [16-17]. Yi et al. [18] established that the wear resistance of Fe-B alloy with higher carbon and boron content was comparable to that of high-chromium cast iron. Similarly, Ma et al. [19] discovered that Fe-B alloy with 3.5 wt.%B exhibited excellent corrosion resistance compared to 1Cr18Ni9Ti stainless steel. However, the role of B as a microalloying element in carburized steel is unclear due to its large addition amount in those Fe-B alloys.