Introduction of Nitrided M50 and M50NiL Bearings Into Jet Engine Mainshaft Applications

Rhoads, Mark; Johnson, Mike; Miedema, Keith; Scheetz, Jon; Williams, Jeff

doi:10.1520/stp158020140070

Cited by 8 publications

(1 citation statement)

References 5 publications

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“…Ooi et al reported that duplex hardening treatment can increase surface compression stress and therefore improve rolling contact fatigue resistance of the M50 components [3]. Rhoads M50 to HV 1000~1250 and prolonged the rolling contact fatigue life by 8~10 times with duplex hardening [4]. Streit et al reported that duplex-hardened M50 bearings had lower spall propagation rates over conventional counterparts in low or boundary lubrication conditions and contaminated lubrication conditions due to the high surface hardness [5].…”

Section: Introductionmentioning

confidence: 99%

A Novel Decarburizing-Nitriding Treatment of Carburized/through-Hardened Bearing Steel towards Enhanced Nitriding Kinetics and Microstructure Refinement

et al. 2021

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Decarburization is generally avoided as it is reckoned to be a process detrimental to material surface properties. Based on the idea of duplex surface engineering, i.e., nitriding the case-hardened or through-hardened bearing steels for enhanced surface performance, this work deliberately applied decarburization prior to plasma nitriding to cancel the softening effect of decarburizing with nitriding and at the same time to significantly promote the nitriding kinetics. To manifest the applicability of this innovative duplex process, low-carbon M50NiL and high-carbon M50 bearing steels were adopted in this work. The influence of decarburization on microstructures and growth kinetics of the nitrided layer over the decarburized layer is investigated. The metallographic analysis of the nitrided layer thickness indicates that high carbon content can hinder the growth of the nitrided layer, but if a short decarburization is applied prior to nitriding, the thickness of the nitrided layer can be significantly promoted. The analysis of nitriding kinetics shows that decarburization reduces the activation energy for nitrogen diffusion and enhances nitrogen diffusivity. Moreover, the effect of decarburization in air can promote surface microstructure refinement via spinodal decomposition during plasma nitriding.

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Section: Introductionmentioning

confidence: 99%

A Novel Decarburizing-Nitriding Treatment of Carburized/through-Hardened Bearing Steel towards Enhanced Nitriding Kinetics and Microstructure Refinement

et al. 2021

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Chapter 12 | Wear and Debris Contaminant Testing, Lubricant Additive Effects—Tribo-Metallurgy

Beswick¹

2022

Rolling Bearing Steel: Design, Technology, Testing and Measurements

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Rolling bearing steel wear testing and properties are multifaceted. A combination of tribology and related physical metallurgy is summarized in this chapter. ISO 15243-2017 describes rolling bearing damage terms, characteristics and failure origins. Wear failure modes exist in rolling bearings and ASTM G40-21a, Standard Terminology Relating to Wear and Erosion, defines abrasive and adhesive wear. A form of abrasive wear can be observed in rolling bearings operating with contaminated lubricants. The nature of the contaminant is important in steel technology related mitigation measures. For example, metallic contaminants result in different raceway tribology characteristics as compared to abrasive contaminants. Three-body abrasive wear properties can be critical in aviation rolling bearing steels and for this reason appropriate bearing steel, cage steel, and alumina abrasive tests have been developed. Adhesive wear can occur if the lubricant film thickness is insufficient. The factors influencing the occurrence of adhesive wear are defined and microstructure and the steel heat treated hardness are key parameters. Traction coefficient measures are used particularly for assessment of the steel technology combinations such as rolling element materials and stainless carburized steel rolling contacts. Sliding wear, micropitting, and macropitting properties may be assessed using standard tests, and such tests are of importance in integrated rolling bearing and gear products. Applications involving slip in the contacts requires specific tribology testing and as such near surface hardness is important. Raceway surface solid contaminant effects are studied using indent tests. Raceway artificial dents are often used and predented contaminate tests can be applied to test rolling contact fatigue strength in the presence of raceway indentation. Such raceway surface damage may be classified as surface distress, the most common failure mode in modern rolling bearings. The use of extreme pressure (EP) additives can have a profound effect on the rolling bearing steel tribo-system.

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Chapter 17 | Super-Precision Aerospace Bearing Steel Technologies

Beswick¹

2022

Rolling Bearing Steel: Design, Technology, Testing and Measurements

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Steel technologies used in precision aerobearings are unlike those used in industrial machines or automotive rolling bearings, etc. Quality assurance, with respect to metallurgical cleanliness, is achieved by the use of multiple vacuum steelmaking and a revised ASTM E45 micro-inclusion rating method. Vacuum induction melting (VIM) in combination with vacuum arc remelting (VAR) is the mostly applied steelmaking method. Aeroengine rolling bearings typically run at elevated temperatures. In order to achieve the required high temperature, hot hardness requirements, secondary hardening steels such as M50 (through hardening) and M50NiL (case carburizing) steels are employed. In addition to M50 and M50 NiL, other aerobearing steel grades and heat treatments are applied especially when resistance to corrosion is required. Advanced high-speed steel compositions such as 7-7-7-11 (Aerospace Materials Specifications, AMS 6560), using powder metallurgy manufacturing methods, are increasingly being applied. The super precision aerobearing market requires numerous types, and sizes, of relatively exotic bearing rings and are produced in small batches. Application loads and lifecycle requirements means that forging with rolling bearing raceway conforming material flow conformance are specified in the design. Due to the use of VIM-VAR or other remelt steelmaking, “classical” subsurface inclusion initiated spalling is usually not observed. Aerobearing ring and rolling elements often have to tolerate lubricant contamination. The failure mode is thus surface distress and for this reason surface strengthening heat treatments have been developed and used. Nitriding of the steel ring working contact surfaces is often applied especially in combination with silicon nitride rolling elements. Corrosion resistance is recognized as a requirement in aeroengine bearings especially when engines are intermittently used (i.e., standstill corrosion conditions). Corrosion resistant bearing steel development and testing is a demanding topic (see Chapter 10). Functional test results on various “standard” and newly developed aerobearing steel technologies are published in ASTM STPs.

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Introduction of Nitrided M50 and M50NiL Bearings Into Jet Engine Mainshaft Applications

Cited by 8 publications

References 5 publications

A Novel Decarburizing-Nitriding Treatment of Carburized/through-Hardened Bearing Steel towards Enhanced Nitriding Kinetics and Microstructure Refinement

A Novel Decarburizing-Nitriding Treatment of Carburized/through-Hardened Bearing Steel towards Enhanced Nitriding Kinetics and Microstructure Refinement

Chapter 12 | Wear and Debris Contaminant Testing, Lubricant Additive Effects—Tribo-Metallurgy

Chapter 17 | Super-Precision Aerospace Bearing Steel Technologies

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