Development of a powder metallurgical corrosion-resistant bearing steel containing NbC and its transfer to industrial applications

In this work, a new powder metallurgical corrosion-resistant bearing steel containing NbC was developed based on thermodynamical equilibrium calculations using CALPHAD (CALculation of Phase Diagrams) methods. Starting with conventionally cast test melts, a processing route, known as diffusion alloying, was used to achieve a fine dispersion of the NbC. Two different alloys were used to reveal the influence of nickel and cobalt on the system. The resulting properties led to the choice of the alloy containing cobalt for industrial production. The complex processing route was continuously optimised for this purpose. In addition, the heat treatment was adjusted to simultaneously achieve a high hardness and a high corrosion resistance. The promising laboratory results led to the manufacture of bearings, which were investigated in bearing lifetime tests to estimate their usability for applications in seawater.