Effect of Nb content on microstructure, friction and wear properties of Fe-25Mn-9Al-8Ni-1C-xNb alloy

In order to reveal the failure mechanism of diesel engine cylinder head materials under harsh working conditions and further improve the service performance of materials under harsh working conditions, we have studied Fe-25Mn-9Al-8Ni-1C-xNb alloy. In this paper, Fe-25Mn-9Al-8Ni-1C-xNb(x = 0, 0.1, 0.2, 0.3, 0.4) alloy was prepared by vacuum non-consumable electric arc furnace. The microstructure and friction and wear properties of the alloy under three different working conditions (dry friction, oil lubrication and sulfur boundary lubrication) were studied. The results show that Fe-25Mn-9Al-8Ni-1C alloy is composed of austenite phase and k-carbide phase, while Fe-25Mn-9Al-8Ni-1C-xNb alloy is composed of austenite phase, ferrite phase and NiAl intermetallic compound. With the increase of Nb content, the average friction coefficient and volume wear rate of the alloy decreased gradually under different working conditions. Especially, the average friction coefficient and volume wear rate of Fe-25Mn-9Al-8Ni-1C-0.4Nb alloy reach the minimum. Under the condition of sulfur boundary lubrication, the average friction coefficient and volume wear rate of Fe-25Mn-9Al-8Ni-1C-0.4Nb alloy are 0.061 and 0.23 × 10 −4 mm 3 N −1 m −1 , respectively, which are 82.7% and 97.3% lower than that of the base alloy under the condition of dry friction. It is attributed to the formation of hard phase NbC which can resist wear after the addition of Nb element, and the formation of layered FeS with lubricating effect on the worn surface.