Evaluation of Tribological Behaviors of Lightweight Crosshead Materials in a Reciprocating Plunger Pump

Lightweight design is crucial for reducing inertial forces and vibrations in high-power-density reciprocating plunger pumps (RPPs). However, the tribological compatibility of lightweight alloys for crosshead–liner tribo-pairs is not well understood. This study systematically evaluates the friction and wear behaviors of six lightweight materials (TC4, TC4 (MAO), TC11, TC18, ZL108, and AlSi10Mg) sliding against HT250 gray cast iron under different lubrication conditions using an SRV IV tribometer. The results show that the lubrication regime significantly affects tribological performance. Water lubrication led to severe abrasive wear and high friction coefficients (0.75–0.91), while oil lubrication reduced friction to around 0.20 and promoted the formation of protective boundary films rich in P, S, and Zn. Material selection played a key role in wear mechanisms: aluminum alloys performed better under oil lubrication, whereas titanium alloys were more stable under water-lubricated conditions. MAO treatment on TC4 improved wear resistance, reducing the wear weight to less than 0.3 mg under oil lubrication by creating a strong ceramic oxide layer. Negative wear rates in lower specimens indicated material transfer from the upper specimen to the lower specimen. Based on performance metrics, the TC4-MAO/Shell 220 combination is recommended for lightweight crosshead applications. This study offers insights and guidelines for material selection to enhance the reliability and efficiency of future hydraulic equipment.