Abstract
Dies with narrow and deep gaps, made from AISI H10 die steel, were nitrided by various manufacturers of equipment for ionic and gas nitriding. The manufacturers themselves, based on their experience with extrusion dies, chose the optimal nitriding parameters. The microstructure obtained showed differences with regard to the presence or absence of a compound layer, its thickness and ε/γ' phase ratio (XRD), nitriding depth and microhardness values. The nitriding depths obtained, the maximum microhardness of the nitrided surfaces and ε/γ' phase ratio were usually similar on dies of the same manufacturer, while for different die manufacturers these values differ. Samples with the various nitrided microstructures mentioned were laboratory tested for wear resistance by a newly designed test rig that provided simulation of the tribological conditions of hot extrusion of aluminium. The results of the study indicate that dies with a greater nitriding depth (diffusion zone) in combination with a compound layer mainly composed of only one phase (in our case ε phase) exhibited better wear resistance than those with a lower nitriding depth and with an equal share of the two phases.
