PLASMA NITRIDING OF POWDER METAL STEEL

The influence of plasma nitriding conditions (temperature, process duration, gas mixture, pressure) on the surface layer microstructure and on the compound and diffusion layer properties at the surface of chromium alloyed powder metal steel samples has been studied. A rather high surface hardness of 710 HV 5 and 890 HV 0.3 is achieved. This is a consequence of the compound layer being formed very rapidly as a result of a high content of alloying elements in the powder metal steel matrix. The nitriding layer grows in accordance with the diffusion nature of the nitriding process reaching 200 and 700 μm after 3 and 16 h, respectively. In spite of the fact that the diffusion layer continues to grow steadily with the time, the compound layer thickness reaches a saturation level after only 6 h of around 7 μm. The compound layer is continuous over the entire surface of the samples, including voids, thus giving rise to potentially very good wear properties. © 1990.