Reactive boundary layers in metallic rolling contacts

• Applicant: Dr.-Ing. Mathias Woydt
• Subject Area: Engineering Design, Machine Elements, Product Development
• Term: from 2011 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 200430163

To date there is insufficient knowledge of the mechanisms and parameters that induce tribologically favorable layers, generated during running-in, in tribo-technical systems. These very thin layers formed by friction processes in the contact area are known in the literature as Beilby- or Cervovit-layers. It was shown during the initial two years of funding that wear can be reduced by implementing a pre-conditioning regime involving either modified lubricants or cold work hardening. A strong reduction in friction has yet to be seen, though no increases as a result of pre-conditioning were observed. A reduction in friction through new lubricant additives like amine phosphate, dibenzyl disulphide or bismuth tris(dimethyldithiocarbamate) (up to this point Modttc and inorganic additives) and pre-conditioning time reduction from 10,000 to 1,000 cycles will be explored within the scope of the current project application. Other applied substances, e.g. serpentines, will be introduced in combination with these additives to ensure improvements to wear resistance of generated tribofilms. The ultimate goal is to yield a simultaneously cold work hardened (at Hertzian contact pressures above Pmax = 3.0 GPa, without surface a damage) and tribofilm (generated from appropriate lubricant formulations) protected steel surface substrates that can ultimately replace thermochemically treated steels. Reducing friction, followed by ecotoxicologically acceptable additives, is paramount to this proposal. Steels prepared with the two proven pre-conditioning methods, cold work hardening and tribofilm generation, will be subjected to slip-rolling endurance testing under boundary friction, run up to 10E7 cycles. Their friction and wear behaviour will be characterized.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1551: Resource Efficient Constructional Elements