On the Presence of Eta Carbide in the Cryogenically Treated High Speed Steel

Abstract

The research in the cryogenic treatment of tool steels and other alloy steels is important as it causes substantial increase in the wear characteristics of alloy and tool steels. The present day research of this technology indicates precipitation of submicroscopic carbides referred to as eta carbides. This work comprises of reviewing the carbide types that form during heat treatment of high speed steels and presenting the results of the experiment for finding eta carbide in the cryogenically treated AISI T42 high speed steels using advanced microscopy. The results of this work indicate the contribution from the other secondary carbides (other than eta carbides) in the enhancement of wear characteristics in high speed steels.

Microstructure of Tool Steel X37CrMoV5 after Cryogenic Treatment and its Effect on Wear Resistance

“…Several modifications were identified in tool and high speed steels. Carbide Fe 3 Mo 3 C prevailed in cryogenically treated high speed steel after low-temperature tempering up to 200°C [11]. Phase M 6 C can be characterized by an fcc elementary cell with 96 metal sites, which are occupied with iron and molybdenum, and 16 carbon sites.…”

“…In such a complicated microstructure it was difficult to find another fine secondary precipitate --carbide, which could precipitate as a result of cryogenic treatment [1,20]. It has been published that -carbide can precipitate in plain high carbon steel after deep freezing and subsequent tempering at temperatures up to 200°C, i. e. in the initial stages of tempering [11]. It was also found, that wear resistance could be improved after the cryogenic treatment, which included DCT and tempering in a temperature range from 150 to 200°C [4,12,17].…”

“…Multiple tempering after cryogenic treatment enhances the dimensional stability and reduces the residual stresses [3]. Cryogenic treatment has been applied to cold-working tool steels [5,6,7], powder-metallurgy steels [8,9], high speed steels [10][11][12][13][14], structural steels [15,16] and also cast iron [17,18]. Although a lot of work has been done concerning the cryogenic treatment of steels, the mechanism of the structural changes, which result in significant improvement of wear resistance, is not yet fully understood.…”