The Development of Bearing Steels with Long Life and High Corrosion Resistance

Abstract

The operating environments of rolling bearings are remarkably varied. With the use of bearings in various corrosive environments increasing, interest in stainless steel is growing. AISI 440C has been widely used in applications where corrosion resistance is of primary concern. However, its performance has not always been satisfactory because it contains coarse eutectic carbides that act as crack initiators under rolling contact stress and reduce Cr content in the martensitic matrix to the carbides. In response, we performed research to determine the most suitable bearing steel composition for both long fatigue life and noise performance and high corrosion resistance. Carbide size and hardness comparable to AISI 52100 steel were essential for the new stainless bearing steel(ES1), so we lowered the carbon and chromium contents and increased the nitrogen content of AISI440C. To control production costs, we applied conventional steelmaking processes for the nitrogen alloying. We evaluated the fatigue life and corrosion resistance of the new bearing steel(ES1). The new steel(ES1) outperformed conventional martensitic stainless steels in a tap water immersion test, a 5% aqueous sodium chloride immersion test, a saltwater spray test, noise level measuring test, water submerge life test, and oil lubrication life test.

An updated review: White etching cracks (WECs) and axial cracks in wind turbine gearbox bearings

“…However, compared with AISI 52100, the dynamic load bearing capacity is lower and the steel contains coarse eutectic carbides (up to 60 μm) which can act as crack initiators and chromium concentration sites. 128,198 Martensitic stainless steel ES1 164,198 has a lower carbon and chromium content than AISI 440C to suppress eutectic carbides and has a comparable hardness to AISI 52100. M50 (through or case hardened) and M50NiL (case hardened) are secondary hardening steels with alloy carbides (Cr, Mo and V) more stable than cementite, are vacuum-induction remelted vacuum arc remelted (VIM-VAR) manufactured to reduced oxygen content and therefore non-metallic inclusions, and display a much reduced tendency to form WEA (butterflies) under normal operation loads.…”

White structure flaking (WSF) in wind turbine gearbox bearings: Effects of ‘butterflies’ and white etching cracks (WECs)

“…However, compared with AISI 52100, the dynamic load bearing capacity is lower and the steel contains coarse eutectic carbides which can act as crack initiators and chromium concentration sites. 80,84 Martensitic stainless steel ES1 51,84 has a lower carbon and chromium content than AISI 440C to suppress eutectic carbides and has a comparable hardness to AISI 52100. ES1 is alloyed with nitrogen which forms carbonitrides, strengthens the matrix and provides corrosion resistance, all the above enabling a tenfold increased WSF life compared with AISI 52100.…”

Effect of Substituting Ni by N on Corrosion Behavior of Stainless Steel

“…Also, many authors concluded that alloying stainless steel with N has a positive effect on general corrosion resistance. At the same time, it unambiguously improves the local corrosion resistance (stress corrosion cracking, pitting, intracrystalline corrosion, and crevice corrosion) [8][9][10][11][12]. According to the results obtained by Sakamut et al [13], increasing the content of N from 0.1 to 0.38 in austenitic stainless steel decreases corrosion rates in boiling 5% H2SO4 solution and in 10% HCl solution at a temperature of 25C.…”

“…Increasing of N from 0.06% to 0.18% in stainless steel grades -(20% Cr, 25% Ni), and (20% Cr, 25% Ni, 4.5% Mo) decreased the passive current density when tested in HCl and H2SO4 acids [16]. Speidel and others [8][9][10][11][12]17] interpreted the corrosion resistance of stainless-steel grades. They found that N dissolved in corrosion medium to form NH3, which increased pH and hence retarded the electrolyte at less acidic pit sites.…”