Speaker
Description
Forming industry is confronted with ever increasing demands on productivity, quality and performance of tools and dies. The main limiting factors are wear and fatigue resistance. Good abrasive wear resistance is obtained by increasing material hardness, which however may hamper toughness and fatigue resistance. Therefore different surface engineering techniques like plasma nitriding are used to form hard surface layers with high wear and corrosion resistance while preserving core toughness. Thickness and properties of the nitride layer depend on the steel composition and nitriding parameters (temperature, time, gas mixture) and is limited to few hundred microns. Deep cryogenic treatment (DCT) is another heat treatment of tool steels gaining attention in recent years. Normally it is combined with the traditional heat treatment, where after quenching material is exposed to cryogenic temperatures below -160 °C, usually by immersion into liquid nitrogen, and then followed by tempering. DCT facilitates transformation of retained austenite into martensite, induces precipitation of additional carbides and modifies their distribution and size, thus providing improved toughness and fatigue resistance while maintaining high hardness. The aim of our work was to investigate the mutual effect of DCT and plasma nitriding on the formation and properties of the nitrided layer as well as the resulting wear and fatigue resistance of EN 1.2367 Chrome–Molybdenum–Vanadium hot work tool steel. Investigation comprised metallographic analysis, XPS, ToF-SIMS, hardness depth profiling, abrasive wear resistance under dry reciprocating sliding contact (pin-on-disc configuration) and bending fatigue resistance. Results clearly indicate enhancing effect of DCT.
Keywords: plasma nitriding, deep cryogenic treatment, tool steel, wear, fatigue
| Speaker Country | Slovenia |
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