Tool steels produced with powder metallurgy (P/M) are perspective materials, although they are more expensive in comparison with tool steels produced with the conventional method. The work focuses on the study of mechanical properties and structure depending on the heat-treatment conditions for the two tool steels. These are the 1.2379 steel for cold work produced with classical metallurgy and high-speed P/M steel Vanadis 23. Both materials were heat treated in the conventional manner to achieve a hardness of 61 HRC. They were also exposed to a cryogenic treatment at temperatures of -90°C and -196°C for 4 h between the hardening and the tempering. We evaluated the hardness and strength using the three-point-bending test and the wear resistance using the pin-on-disk method. Keywords: powder metallurgy, high-speed steels, heat treatment, cryogenic treatment, wear rate Orodna jekla, proizvedena s postopki metalurgije v prahu (angl. P/M) so perspektivni materiali, kljub temu da so dra`ji od tistih izdelanih s konvencionalno metodo. Delo je osredoto~eno na {tudijo mehanskih lastnosti in strukturo, v odvisnosti od pogojev toplotne obdelave za ti dve vrsti orodnih jekel. To so jekla 1.2379 za delo v hladnem, proizvedena s klasi~nimi metalur{kimi postopki in hitrorezno P/M jeklo Vanadis 23. Oba materiala sta bila toplotno obdelana s konvencionalnimi postopki, glede na njuno sestavo, tako, da sta dosegli trdnost 61 HRC. Bili sta tudi izpostavljeni obdelavi s podhlajevanjem pri temperaturah od -90°C in -196°C za 4 h med strjevanjem in temperiranjem. Trdnost je bila ocenjena pri trito~kovnem mehanskem testu (zvijanje) in s testom obrabe po metodi pin-on-disk. Klju~ne besede: metalurgija prahov, visokorezna jekla, toplotna obdelava, obdelava s podhlajevanjem, stopnja obrabe

Sub-zero treatment of tool steels is included within the cycle of conventional heat treatment. This kind of heat treatment has been reported to improve wear resistance of tools. The improvement is attributed to precipitation of fine carbide particles, but is depending on a number of the other factors as well. This paper follows the previous works, in which the effect of sub-zero treatment on the mechanical and structural properties of P/M tool steels was evaluated. Two types of P/M cold work tool steels were used in the research: Vanadis 6 and high speed steel Vanadis 30. They were austenitized, nitrogen gas quenched and tempered. The 4 hours long sub-zero period of dwell at -196°C was also incorporated between quenching and tempering. Wear evaluation was carried out using a pin-on-disk method.The observed values of wear resistance have been collated with the values of hardness and the bending strength. The results of the work are supplemented by a detailed analysis of the carbide particles of both monitored conditions.

The paper deals with the assessment of the effect of content of cobalt and cryogenic treatment on mechanical properties and structure of Vanadis 23 and Vanadis 30 PM high-speed steels. The studied characteristics are evaluated after conventional heat treatment (quenching and multiple tempering) and also when deep cryogenic treatment at -196°C/4 hours was inserted between quenching and tempering. The mechanical properties are assessed by a three-point bending flexural test and by measurement of the hardness. Metallographic analysis is performed using an energy dispersive spectrometer (EDS) and the scanning electron microscope (SEM).