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SUMMARY
The paper deals with cryogenic treatment and nitriding process combined with succesive cryogenic treatment of forging dies made of tool steels. In differentiation from traditional cold treatment of steel, usually performed for a couple of hours at approx. -70°C, cryogenic treatment was performed for tens of hours at approx. -180°C. Authors made an attempt to explain the way of microstructural changes during cryogenic treatment by means of the dilatometric tests and differential thermal analyses (DTA) of specimen. Furthermore comparative characterization of specimens with and without cryogenic treatment was made. Characterization included the effect of cryogenic treatment on such parameters as wear resistance at elevated temperature and hardness of hot-work steels. Results confirming an increase of lifetime of tested forging dies after cryogenic treatment and after nitriding combined with succesive cryogenic treatment are presented.
Keywords
Long-term cryogenic treatment, gas nitriding, tool steels, forging dies, hardness, wear.
1 Instytut Mechaniki Precyzyjnej, Warszawa
