The effect of chromium in high carbon bearing steels

The Cementite Spheroidization Process in High-Carbon Steels with Different Chromium Contents

“…By analyzing the transition lines for the different alloys, the right cementite particle spacing (the combination of the austenitization temperature and time) and the cooling rate can be chosen without performing a range of long experiments in order to successfully obtain spheroidized structures. For instance, the pearlite-promoting effect of Mn experimentally observed in the literature [5,12] can now also be predicted using the described approach (Figure 7(b)). …”

“…Although the existence of the DET reaction has been known for years, only a limited number of studies of the mechanism and especially of the effect of alloying elements on the DET reaction are available. The work has mainly been performed on SAE 52100 bearing steel, [3][4][5][6][7][8][9][10][11][12] for which the achievement of a well-spheroidized structure is necessary before the subsequent machining and further bainitic or martensitic heat treatment. [15,16] This work has shown that a change in Cr content in hypereutectoid steels has a significant influence on the cementite spheroidization process.…”

“…The austenitization of high-Cr steels can be performed at higher temperatures without the promotion of the pearlitic reaction, which is opposite to the effect of Mn experimentally found by Verhoeven [5] and Beswick. [12] It is possibly not only due to an increase of the A¢ 1 temperature with Cr content, but also because Cr is a very strong carbide former leading to a sufficient amount of cementite even at austenitization temperatures as high as A¢ 1 + 75 K, and coarsening/dissolution of cementite is slower due to Cr additions. The advantage of using such high austenitization temperatures is the increased possibility to dissolve the grain-boundary cementite network present in the initial pearlitic microstructure.…”

“…In Cr-free steel pearlite formation has been observed even after low-temperature intercritical austenitization. Beswick [12] has studied the effect of Cr in bearing steels by lowering its content from 1.42 wt pct (SAE 52100 steel) to 0.03 wt pct and demonstrated that a decrease in Cr content in hypereutectoid steels influences the carbide particle size. The experiment to obtain a similar spheroidized structure with different Cr contents was not fully successful, and the finer microstructure in steels with higher Cr content was explained from the finer initial pearlite lamellae spacing.…”

Carbon Redistribution in Martensite in High-C Steel: Atomic-Scale Characterization and Modelling

“…Stormvinter et al [5] found the formation of transformation twins in martensite substructures in both 1.2 wt% C and 1.67 wt% C steels by TEM characterization. The twinned plate martensite was observed by Beswick [16] in 100Cr6 steel in the as-quenched state after austenitization at 850 • C for 15 min. Recently, Li et al [6] observed the C segregation at the nanosized twin boundaries in white etching areas (after a rolling test for 2 h with 2.7 × 10 7 rolling cycles) in a martensitic 100Cr6 bearing steel by APT characterization.…”