Reaktionsschichtbildung auf bleifreien Bronze- und Messingwerkstoffen im Kontakt von Zylinder und Steuerscheibe einer Axialkolbenpumpe

  • Tribolayer Formation on Lead-Free Bronze and Brass Materials in the Contact between Cylinder and Valve Plate in an Axial Piston Pump

Paulus, Andreas; Jacobs, Georg (Thesis advisor); Murrenhoff, Hubertus (Thesis advisor)

Aachen (2017)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2017

Abstract

The purpose of this work is to replace the lead-containing alloy by lead-free alloys in thecontact between the cylinder and the valve plate of an axial piston pump. This has to beachived without loss in performance or service life of the axial piston pump. In order toachieve this goal, the wear-reducing effect of the lead content in the surface region of thematerial has to be substituted. One possibility for this is the targeted generation of functionalsurface layers (so-called boundary layers), which are caused by a tribological load, incombination with lubricants. Those layers can reduce both friction and wear in gears androlling bearings.Within the scope of this study, experiments have shown that boundary layers are alsogenerated in lubricated sliding contacts on bronze and brass materials and can reduce frictionand wear. A methodology has been developed with the aid of which it is possible to examinecertain tribological systems with regard to the formation and effect of boundary layers. Thismethodology has been successfully applied to replace the lead-containing bronze in thecontact between the cylinder and the valve plate in an axial piston pump by a lead-free bronzeor brass material.After the analysis of the tribological system and the definition of suitable replacementsystems, five lead-free bronze and brass materials as well as two additivated lubricants wereinvestigated. In addition to experimental model and component tests, the boundary layerswere analyzed systematically in microanalytical investigations.The lead-free alloy CuSn12Ni2 was qualified in the tests as a possible alternative to the leadcontainingseries alloy. The positive properties of the CuSn12Ni2 alloy are based, inter alia,on the formation of a stable boundary layer in operation, which can be investigated andcontrolled using the methodology presented here.