Aspects of tribological surface design with particular reference to the effects of low pressure nitriding and residual stresses in rolling contacts

Methods for the design of surface layers and coatings for machine pairs operating under mechanical and thermal loads are discussed. The influence of a low-pressure nitriding process on the state of the residual stresses in the surface layers of M2 steel has been investigated. The database of the residual stress distribution in the surface layer with use of the Waisman–Phillips method was elaborated and verified by sin2ψ X-ray method. On the basis of the example of a cam mechanism of a injection pump, the numerical model for superposing the residual stresses and those coming from the external loads is shown. The simulation was made by means of the Finite Element Method and the standard program ANSYS 5.4. The criteria of the occurrence of particular contact wear shapes (normal and abnormal) were defined on the basis of the simulated stress distribution analysis. The results of the modelling were verified by observation the injection pumps, both in an in-house test and in field tests. A new, quantitative, way of the determination of the nitrided layer structure, and boundaries of its tolerance for actual operating conditions under concentrated contact stresses is proposed.