Oberflächenermüdung von nitrierten, einsatz- und durchgehärteten Werkstoffen

Research output: ThesisDoctoral Thesis

Abstract

For various machine components such as roller bearings, gears, etc. different local damage mechanism (adhesion, abrasion, pitting, etc.) occur on the contact surface. These mechanisms affect increasingly the function of the parts or even lead to tribological as well as cyclic mechanic failure of the parts during their operation. These damages are caused either by material wear or by material fatigue below the surface. The present work examines the influence and differences of case hardened and plasma nitrided materials with respect to load-carrying capacity through rolling contact tests, damage analysis and finite elements simulations. The case hardened, plasma nitrided and quenched layers are characterised for their suitability for cyclic rolling contact loads. By preparation of a damage model for point and line contact, the technological layer treatment is connected with the experimentally determined damages and the numerically determined amount of stress. The determination and applicability of a two stage S/N curve model without distinct fatigue level are provided by numerous tests. Recommendations for the technological and economic limitation of the case hardened and nitrided depth of the layers are formulated in this work. Comprehensive metallographic tests as well as residual stress and residual austenite measurement for the discussion of material change under rolling contact load complete this work. It should be mentioned that the rolling contact fatigue suitability can, by no means, be deduced from dynamic S/N characteristic value. This is due to the fact that the material stress must be connected with the local rolling contact load, which is dependent on the progress of local contact pressure and slip.

Details

Translated title of the contributionRolling contact fatigue of nitrided, case-hardened and quenched specimens
Original languageGerman
QualificationDr.mont.
Supervisors/Advisors
Publication statusPublished - 2012