Temperature control during the APN-process on the steel 1.3343

摘要

Nitride layers on the high-speed steel 1.3343 were produced by means of transmitted plasma arc. The surface treatment with plasma arc leads to high thermal stress reliefs caused by the tracing point of the arc. To use the plasma arc to build up a nitrided layer without a deep heat penetration of the base metal requires a good knowledge of the temperature profile on and under the surface. The investigations show that the steel needs a stable temperature on the surface to reach maximum nitrogen input. At the same time the surface temperature must not reach the melting point of the material. To satisfy these two conflicting conditions an accurate temperature control is necessary. Surface temperatures, temperatures in the bulk and under the surface were measured by conductive and thermographic methods and were correlated with investigations of the resulting metallographic structure. It was shown that the temperature distribution in and under the surface zone during the atmospheric plasma-nitriding shows a large gradient and the material temperature at a depth of 100 μm is not more than 200 °C.