Synergistic effects of surface heat treatment and friction modifiers on the wear resistance of QT tribo-pairs under boundary lubrication conditions

Vollständiger Abstract

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Purpose Plunger pairs in emulsion pumps typically operate under extreme boundary lubrication conditions, resulting in severe wear issues. Existing studies have often examined material selection, heat treatment and lubrication independently, without adequately addressing their synergistic interactions. To bridge this gap, this work aims to systematically investigate the combined influence of these factors on tribological performance. Design/methodology/approach Using QT600 and QT400 ductile irons, specimens with varying hardness were prepared through heat treatment and subsequently paired with nitrided counterparts. Tribological tests were performed under simulated service conditions using gear oil containing 1.5 Wt.% molybdenum dialkyldithiophosphate. Wear mechanisms were characterized via scanning electron microscopy and energy dispersive spectroscopy. Findings The results indicate that the nitrided layer underwent microfracture and delamination, which aggravated abrasive wear. In contrast, heat treatment significantly enhanced wear resistance. The most favorable performance was observed when the spherical specimen possessed higher hardness than the disc specimen, a configuration that stabilized contact conditions and facilitated the formation of a protective tribofilm. Originality/value This study highlights the critical roles of mechanical compatibility and surface-lubricant synergy in wear mitigation, demonstrating that tailored heat treatment can effectively optimize the performance of friction pairs and inform the design of advanced lubrication systems. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-03-2026-0110/