Low density steel 1·2C–1·5Cr–5Al designed for bearings

Abstract

A novel alloy design, designated as 1·2C–1·5Cr–5Al, has been proposed with high aluminium(∼5 wt-) and more carbon(∼1·2 wt-) addition into the classical 1C–1·5Cr bearing steel for lowering density and improving performance simultaneously, which is approximate 8 wt- lighter than convention. In order to understand preliminarily the suitability of the novel alloy for bearing application, the martensite starting temperature and hardness, related to microstructure evolution and mechanical properties, respectively, after partial austenitisation treatment with undissolved carbides have been investigated carefully. The martensite starting temperature is comparable with conventional 1C–1·5Cr alloy. The hardness of 860±3 HV20 achieved is much higher than convention.

Martensitic transformation cracking in high carbon steels for bearings

“…The initial microstructure of the ‘1.2C–1.5Cr–5Al’ alloy in hot-rolled condition consists of almost full pearlite due to its near eutectoid composition, 4 while the ‘1C–1.5Cr’ steel contains both pearlite and proeutectoid cementite networks (Fig. 1).…”

“…The hardness originates from the supersaturated carbon in martensite combined with precipitation hardening of the retained chromium-enriched hard cementite or chromium carbides. 3,4 The large carbon addition into the alloys, however, increases the brittleness of martensite 5 and tends to generate microcracks accompanied with martensite transformation. [6][7][8] A novel low-density steel 1.2C-1.5Cr-5Al (wt-%) 4 was developed for weight saving and better performance for bearings, compared with the 52100 steel.…”

“…3,4 The large carbon addition into the alloys, however, increases the brittleness of martensite 5 and tends to generate microcracks accompanied with martensite transformation. [6][7][8] A novel low-density steel 1.2C-1.5Cr-5Al (wt-%) 4 was developed for weight saving and better performance for bearings, compared with the 52100 steel. High aluminium addition has two effects: (i) reducing the density to approximately 7.1 g cm −3 , ∼8% lighter than conventional bearing steels 4 ; (ii) elevating the martensite start (M S ) temperature and therefore can compensate the M S temperature decrease due to the extra carbon addition.…”

“…A novel low-density steel 1.2C–1.5Cr–5Al (wt-%) 4 was developed for weight saving and better performance for bearings, compared with the 52100 steel. High aluminium addition has two effects: (i) reducing the density to approximately 7.1 g cm −3 , ∼8% lighter than conventional bearing steels 4 ; (ii) elevating the martensite start ( M S ) temperature and therefore can compensate the M S temperature decrease due to the extra carbon addition. The combined addition of 5 wt-% of aluminium and 1.2 wt-% of carbon maintains the alloy to have similar M S temperature and consequently similar martensite fraction in as-quenched conditions compared with typical 52100 steels.…”

Mechanical Properties of High Carbon Low-Density Steels

“…In our paper, two types of steels are presented, which are based on the alloying concepts presented in [ 15 , 16 , 17 ] and modified so that their heat treatment can be carried out efficiently to achieve the required strength and deformation characteristics. The aim is to achieve a yield strength to ultimate strength ratio of max.…”