The effect of sub-zero treatments on dry sliding wear performance of Vanadis 6 tool steel was investigated by pin-ondisc tests against three counterpart types: alumina, 100Cr6 ball bearing steel, and CuSn6 bronze. The microstructure of the examined steel consists of tempered martensitic matrix with very small amounts of retained austenite, and three carbide types. Sub-zero treatments increase the carbides count. The hardness of the steel increases with increasing the austenitizing temperature but slightly decreases with the application of sub-zero treatments. Sub-zero treatments affect the wear performance of the Vanadis 6 steel when tempered at the secondary hardening peak as follows: almost no effect of this kind of treatment was detected when alumina was used as a counterpart but moderate amelioration was recorded when either 100Cr6 steel or CuSn6 bronze was used in the sliding couple. This behaviour is attributed to the combined effect of hardness variations and changes in population density of carbides, due to application of sub-zero treatment.
The purpose herein is to assess the impact of different combinations of cryogenic treatments and tempering regimes on tribological properties of Cr–V tool steel against a CuSn6 counterpart. Dry sliding wear experiments are performed using a pin‐on‐disk tribometer according to the Taguchi method. Tribological behavior is investigated under four process parameters at mixed levels: cryotemperatures (−75, −140, or −196 °C), tempering temperatures (170 or 530 °C), sliding velocity (0.064, 0.128, 0.1885 m s−1), and load (1, 5, 10 N). According to the analysis, the minimum friction coefficient is obtained by cryotreatment at −140 °C combined with 170 °C tempering, with a sliding velocity of 0.128 m s−1 and load of 10 N. For the minimum counterpart´s material adhesion level, cryogenic treatment at −196 °C followed by tempering at 530 °C, sliding velocity of 0.1885 m s−1, and applied load of 1 N are the optimum settings. The analysis of variance model shows that the load (39.2%) has statistical significance on the friction coefficient, while the load (59.1%) and tempering temperature (18.0%) have statistical significance on adhesion levels. The tribological behavior of the steel is explained by thorough microstructural examinations using scanning electron microscopy coupled with energy‐dispersive spectroscopy.
Vanadis 6 cold work tool steel was vacuum austenitized, room temperature quenched, differently cryogenically treated (-75, -140 and -196 °C for different durations) and double tempered, at temperatures of either 170 or 530 °C. Galling resistance was assessed by pin-on-disc testing of differently treated specimens against CuSn bronze, at wide ranges of sliding velocities and loads. The obtained results show that cryogenic treatments combined with low temperature tempering improves anti-galling performance of the steel. The best tribological properties were obtained when high-temperature tempering was combined with cryogenic treatment at -196 °C, due to the maximum extent of microstructural alteration generated by this kind of treatment. The improvement in wear performance is accompanied with slight but undisputable increase in corrosion resistance of the steel, at almost no affected toughness as compared with the state after conventional heat treatment. In conclusion, the obtained results imply an opportunity to simultaneously improve wear performance, corrosion resistance and toughness of the examined steel, by choosing a proper combination of cryogenic treatment and tempering.
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