Developing bearing steels combining hydrogen resistance and improved hardness

Szost, B.A., Vegter, R.H. and Rivera-Díaz-del-Castillo, P.E.J. (2013) Developing bearing steels combining hydrogen resistance and improved hardness. Materials and Design, 43, 499-506. (doi:10.1016/j.matdes.2012.07.030).

Abstract

Thermodynamic and kinetic computational modelling are combined to conceive a hydrogen resistant bearing steel. Existing hydrogen resistant steels are not appropriate for bearings due to their low hardness. The proposed microstructure combines a martensitic matrix in which fine cementite precipitates impart strength, and V₄C₃ nano-scaled particles acting as hydrogen traps. It is demonstrated that the conflicting objectives of ultra-hardness and hydrogen resistance can be concealed by: (1) Adding 0.5wt.% V to 100Cr6, which allows to preserve existing steel production technology. (2) Following a novel heat treatment procedure consisting of austenitisation (and a subsequent temperature spike to dissolve coarse V₄C₃), followed by tempering at 600°C where V₄C₃ particles form (and a subsequent temperature spike to dissolve coarse cementite), followed by quench and tempering at 215°C, where fine cementite strengthening particles form. The enhanced trapping capacity of the new steel is demonstrated via thermal desorption; the presence of the desired microstructure after heat treatment is proved via transmission electron microscopy. Concomitant with the trapping ability, a significant hardness increase was observed; this was ascribed to the controlled V₄C₃ precipitation.

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Contributors

Author: P.E.J. Rivera-Díaz-del-Castillo

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