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Effect of deep cryogenic treatment on dilatometric curve and tribological properties of high speed steel

Advantages of deep-cryogenic treatment over standard heat treatment of high speed steels for the purpose of obtaining better exploitation properties are quoted in an increasing number of scientific papers to be found in literature. This paper deals with the improvements of high speed steel properties achieved by using deep-cryogenic treatment on test samples made of the PM S390 MC high speed steel. The effect of deep-cryogenic treatment on the dilatometric curve during tempering and on abrasive and erosion wear resistance has been investigated and compared with results obtained at a set of test samples of the same steel heat treated by conventional method (hardened and three times high temperature tempered). Dilatometric tests confirmed the existence of common processes in tempering, which depend on the initial state of steel (only quenched, and quenched and deep-cryogenically treated). These tests showed that deep cryogenic treatment had not completely eliminated the residual austenite, particularly in the case of the highest austenization temperature. The obtained tribological results confirm that the application of deep cryogenic treatment results in significantly improved erosive wear resistance, while the abrasive wear resistance depends on the applied temperature of austenization.

high speed steel grade PM S390 MC; deep cryogenic treatment; wear resistance

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