Corrosion properties of a plastic mould steel with special focus on the processing route

Abstract

AbstractApplications in plastics processing bear increased requirements for the used materials, especially with respect to their corrosion and wear resistance. For this reason, special powder metallurgical tools steels were developed that fulfil these demands. The common processing route for their production is hot isostatic pressing (HIP) of pre‐alloyed powders which is followed by hot working if semi‐finished parts are to be produced. As an alternative to HIP, super solidus liquid phase sintering (SLPS) permits the consolidation of pre‐alloyed tool steel powders to near net‐shape parts. It can be performed in different sintering atmospheres. In this work, the plastic mould steel X190CrVMo20‐4 was processed by SLPS in vacuum as well as under nitrogen atmosphere. The resulting materials were analysed with respect to their microstructure, tempering behaviour and corrosion resistance in 0.5 molar sulphuric acid in dependence of the heat treatment. As a reference, the HIPed and the HIPed and worked state were also investigated. The results show that different heat treatments alter the ranking of the sintered and the HIPed state with respect to corrosion resistance. As expected, a high tempering for maximum secondary hardness causes a significant loss of corrosion resistance. The experimental findings were supported by thermodynamic calculations based on slight alterations in chemical composition that result from the different manufacturing processes.