Corrosion resistance of plasma nitrided AISI M2 high speed steel

Corrosion resistance of AISI M2 high speed steel samples plasma nitrided in different process gas composition was studied using polarization test. In order to evaluate inherent properties of diffusion zone, the white layer, i.e. compound layer, was removed. Phase structure and surface hardness of samples were characterized using X-Ray diffraction and microhardness tests. Evaluations of polarization curves indicated that plasma nitriding in a gas flow rate of 25 sccm N 2 -75 sccm H 2 improves corrosion resistance of AISI M2 high speed steel, while increasing nitrogen content in gas composition degrades corrosion properties. Metallographic images of corroded surfaces revealed sever pitting corrosion by increasing nitrogen content in the process gas.