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Developing bearing steels combining hydrogen resistance and improved hardness

Research output: Contribution to journalJournal articlepeer-review

Published
<mark>Journal publication date</mark>2013
<mark>Journal</mark>Materials and Design
Volume43
Number of pages8
Pages (from-to)499-506
Publication StatusPublished
<mark>Original language</mark>English

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.