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Eingeladener Vortrag
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The goal of reducing CO2 emissions in the automobile industry has led to the development of increasingly efficient lightweight material solutions that yield enhanced performance. In light of this goal, this current work involves the optimization of the pre-conditioning of novel, high toughness steel bearings without thermo-chemical treatment, with the aim of transferring the running-in phase into the final step of the mechanical finishing process. A case-hardened gear steel and two novel non-case-hardened steels were evaluated.
Downsizing in mechanical systems requires effective lubrication strategies to ensure that increased contact stresses do not cause critical material failure during operation. Additionally, eco-toxicological consideration are becoming increasingly important. In this regard, the goal of this investigation is to transfer the running-in phase into the final step of the mechanical finishing process through the targeted pre-conditioning of novel, high toughness steel bearings without thermo-chemical treatments and compare these to conventional, case-hardened Steels. Pre-conditioning involved implementation of the ecologically sustainable, bismuth-based additives to generate chemically reactive tribofilms on slip-rolling contacts by using a formulation with a high concentration of tribofilm forming additive. Generated tribofilms were analyzed by Raman spectroscopy to elucidate their molecular composition and, ultimately, determine the reaction mechanisms of bismuth-based tribofilm formation. Tribofilm-protected samples were subjected to slip-rolling endurance testing in a factory fill engine oil without pre-conditioning additives to determine the influence of pre-condition tribofilms on friction behavior and wear performance. It was observed that pre-conditioned tribofilms from the bismuth-based additives were able to yield lower coefficients of friction (COF) and profilometric wear coefficients than for Steels without pre-conditioning. Moreover, COF values under mixed/boundary conditions approaching and even less than 0.04 were achieved, thereby rivaling DLC-coated alloy equivalents.