The effect of contact pressure and surface texture on running-in behavior of case carburized steel under boundary lubrication

• Published in: Wear Vol. 376-377; pp. 851 - 857
• Main Authors: Wagner, Jeremy J., Jenson, Alexander D., Sundararajan, Sriram
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.04.2017; Elsevier Science Ltd
• Subjects: Additives; Boundary lubrication; Break-in; Carburizing; Contact pressure; Hardness; Hardness testing; Inspection; Lubricants & lubrication; Lubrication; Pressure dependence; Pressure effects; Run-in; Steel; Surface layers; Surface roughness; Surface texture; Temperature; Time dependence; Ultrasonic testing; Boundary lubrication; Surface texture; Hardness; Break-in; Run-in
• ISSN: 0043-1648; 1873-2577
• DOI: 10.1016/j.wear.2017.02.016

Many engineering tests start with a run-in procedure, as it is commonly accepted that running-in at some fraction of the target load is beneficial due to a reduction in surface roughness. However, the choice of load and duration is often based on historical context or the experience and philosophies of the testing personnel. The objectives of this study were to (1) evaluate the effects of contact pressure and initial composite roughness on the surface evolution during the initial stage of testing, and (2) use this information to determine if there is an optimal load and time for the run-in portion of a test. These tests were conducted with a disc-type machine using carburized steel specimens with a circumferential lay direction and oil with anti-wear additives under specific conditions of slide-to-roll ratio, entraining velocity, oil spin-off temperature, and oil/additive package. The specimen surface was inspected using non-contact profilometery every minute for the first 10minutes of testing, with a subsequently increasing inspection interval for a total of 150minutes. The data demonstrate that the surface roughness reduces within the first few minutes of testing and remains stable for a period of time, which is dependent on the pressure and initial composite roughness. Additionally, hardness measurements indicate that hardness gains are occurring during the test, but over a longer timeframe. •Surface run-in occurs within 5mins, regardless of pressure or initial roughness.•Surface texture lay direction is not a dominant factor in run-in.•Samples showed hardness gains in the contact zone at the end of all of the tests.•If the run-in objective is to make the surface smoother, this happens in minutes.•If the objective is to enhance material properties, longer times may be needed.