The high-speed P/M steel Vanadis 30 was austenitized at 1100 °C, quenched and tempered at various combinations of processing parameters. For one set of specimens, also sub-zero period, made at -196 °C/4 hours between quenching and tempering. The microstructure and mechanical properties have been investigated as a function of austenitizing time, parameters of sub-zero processing and tempering. There were used metallographic analysis, hardness measurement and three point bending test for the evaluation effect of heat treatment conditions to observed materials.

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

The paper evaluates the properties of two cold work tool steels which differ in the production process and content of carbon and vanadium. Both steels are characterized by their great hardenability, toughness, dimensional stability and wear resistance. They are a subledeburitic steel X63CrMoV5-1 produced by classical metallurgy and a ledeburitic steel Vanadis 6 produced by powder metallurgy. Different austenitizing temperatures in the range of recommended values for the material were used during the heat treatment. Both materials were tempered at a temperature of 530 °C. Also cryogenic treatment at temperatures of −196 °C and −180 ° C for 5 h and/or 4 h was inserted into the conventional heat treatment cycle. The effect of the timing of cryogenic treatment in the heat treatment cycle was observed. Hardness measurement, a three-point bending test and a wear resistance test by the pin-on-disk method were used to specify the effect of the conditions of heat treatment on the properties of the investigated materials.

The paper presents the study results of microstructure, phase composition, microhardness and wear resistance of Vanadis-6 tool steel after diffusion boriding and laser processing. In this study the diode laser device was used. As a result of diffusion boriding the obtained surface layers were characterized by needlelike microstructure with good cohesion with the substrate but in the subsurface area delamination and porosity could be observed. Therefore the diffusion boronized layer was processed using laser heat treatment. As a result of influence of the laser beam, three zones were obtained. The remelted zone near the surface, next the heat affected zone and finally steel substrate were observed. The newly created microstructure in the remelted zone consisted of boron-martensite eutectic. Microhardness of boronized layer after laser processing in comparison to the one without laser processing was slightly lower and was approx. from 1300 HV0.1 to 1100 HV0.1. It was found that additional advantage of laser processing of boronized layers was the presence of heat affected zone. This led to obtaining a mild microhardness gradient between the surface and the substrate. The boronized layer after laser processing was characterized by higher wear resistance in comparison to one not subjected to this kind of processing.

The growing pressure on tool performance and durability increases demands on the materials used and on the choice of optimal heat treatment. The properties of tool steels produced by conventional and powder metallurgy (1.2379, Vanadis 23) were compared after different heat treatment modes. Cryogenic treatment was performed in several batches for 4 hours at-90°C or-196°C. Cryogenic treatment was inserted between quenching and tempering. Mechanical properties were evaluated by hardness tests and three-point bending strength and wear resistance by Pin-on-disk tests. Metallographic analysis was performed using light and electron microscopy. On the basis of the results obtained both materials were subject to selected heat treatment and experimental forming tools produced which were used in operation. During operation the wear of the tools (shape change and volume loss) was assessed. Results of the laboratory tests were then compared with operation tests.