Hill Engineering Blog

Presentation: 1st ASTM Bearing and Transmission Steels Technology Symposium

Hill Engineering will be presenting at the upcoming 1st ASTM Bearing and Transmission Steels Technology Symposium in New Orleans, LA on November 2nd through the 16th. We invite you to come see us.

Held at the Sheraton New Orleans Hotel, the objective of the symposium is to bring together rolling bearing and transmission steel practitioners from the steel industries, rolling bearing and transmission product producers, research and development institutes and academia, to present the latest steel technologies and developments.

The abstract for Hill Engineering’s presentation, titled Efficient Residual Stress Quantification in M50NiL Bearing Steel, is included below.

Gas turbine engines rely on bearings and gears as enabling components over a wide range of speeds, temperatures and loads.  In these applications, martensitic steels are the material of choice due to their high strengths and wear resistance. Confirmation of compressive residual stresses at and beneath the surface is a key quality control measure. While this verification is applicable to all aerospace bearings, measuring these stresses is particularly important for case hardened bearings which develop a gradation in hardness and residual stress through heat-treatment. Residual stresses are normally quantified in this scenario using the X-Ray Diffraction (XRD) method coupled with layer removal by electro-polishing to create a profile of residual stress with depth. While this has been the state of the art, it is difficult to precisely control layer removal, electro polishing induces errors by relaxation of the surface stresses, and the whole process is time consuming to accomplish.  In this work, efforts to apply advanced stress release methods, namely slitting and slotting, to a bearing steel are presented. The advantages of both techniques can be seen in low error estimates, higher stress-depth resolution, and faster acquisition time. The test article chosen was a flat disk of M50NiL, a widely used case-carburized bearing steel. XRD measurements from two sources were also obtained on the same part in an attempt to interrogate the repeatability of that method. Good agreement was obtained between all the measurements made as well as with previously published data. Thus, the investigation was continued by executing slotting measurements on actual bearing rings made from M50NiL, and XRD was again performed on these same parts. The similarities and contrasts between the results of the two methods are discussed as well as the challenges surmounted in applying the slotting method to curved surfaces of a relatively hard steel.

If you are planning to attend the conference, please stop by to discuss Hill Engineering’s capabilities in slitting and slotting. For any further information regarding our residual stress measurement capabilities, please contact us.