Abstract
The P/M Vanadis 6 ledeburitic cold work tool steel was heat-treated and plasma nitrided. On processed material, microstructure, hardness and microhardness, nitrogen and carbon concentration depth profiles and phase constitution were investigated. The initial microstructure consists of a martensitic matrix and particles of carbides MC and M₇C₃. After plasma nitriding surface hardness and microhardness were increased due to the nitrogen diffused in the near surface region. Firstly, martensite is saturated with nitrogen. After the solid solubility limit is exceeded, also the MC- and M₇C₃-phases contribute to the total nitrogen uptake of the material. Finally, nitrides like the Fe₄N- and Fe₃N- and CrN-phase, as well as nitride network and continuous compound layer are formed. The possible contribution of each structural constituent to the total nitrogen uptake of the steel is discussed.

Key words
Cr-V ledeburitic steel, heat treatment, nitriding, microstructure, phase constitution

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