Effects of gas carbonitriding process on surface characteristics of new hot working tool steel

Abstract

Gaseous carbonitriding effects on improvement of surface characteristics of new hot working tool steel close to as either chromium AISI H11 or AISI H13 are investigated. Experimental results are related to three aspects: formed layers, microstructure and obtained precipitates. The formed layers are characterised by their basic properties, which are thickness, depth, formed phases, hardness and wear resistance. Microstructure and the diffusion mechanism suggested that high temperature gas carbonitriding process has the potential of improving the mechanical properties with shorter processing time. The arrangement of carbonitrides, nitrides, chromium oxides and retained austenite and Fe₃C carbides allowed obtaining tool performance from the moderate low mass. Microstructural characterisations were performed by metallographic techniques, electron dispersive energy, X-ray diffraction techniques, optical and scanning electron microscopy and glow discharge optical electron spectroscopy. The mechanical properties were assessed mainly by standard hardness and wear tests.

Keywords:

• Carbonitriding
• Wear
• Hardness
• Austenite
• Carbides

The authors are grateful to the technical staff of Ecole des Mines de Saint-Etienne, Centre SMS France (Saint-Etienne, France), for their support and for making available the facilities for various characterisation tests.