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In high-speed and heavy-load mechanical operations, gears are susceptible to pitting, adhesion, and wear, which resulting tooth breakage and wear failure. In this paper, failed gears are subjected to repair experiments through the integration of laser cladding and boriding, and the tribological performances and post-repair vibration characteristics are also systematically investigated. In comparison to the base material, the average hardness of the boride surface exhibited an increase of up to 8.37 times, while the wear resistance increased to 15.60 times. The wear resistance of the repaired gear is 2.62 times that of the normal gear, and its vibration parameters are commensurate with that of the normal gear, which offers empirical substantiation for the enhancement of gear repair and remanufacturing strategies. • The hardness and wear resistance were increased at least 8 times after situ-boriding laser cladding treatment. • After situ-boriding laser cladding, the vibration and impact of the repaired gear were weakened. • Compared with the normal gear, the wear resistance of the repaired gear increased by 2.62 times. [ABSTRACT FROM AUTHOR]

Heat transfer tubes in nuclear power plants are easily damaged by fretting wear. The fretting behaviour of the heat transfer tube related to the lead-bismuth eutectic (LBE) alloys needs to be investigated. In this work, the effect of pre-immersion corrosion in LBE of AISI 316 stainless steel on fretting behaviour is explored in detail. Following short-duration corrosion (specimens denoted C0 and PC1), no significant change occurred during corrosion, and after the fretting test, the wear scars were shallow, with adhesive wear being the dominant wear mechanism. Following long-duration corrosion (specimens denoted PC2 and PC3), the dissolution of Ni and the formation of an oxide layer were the main corrosion mechanisms. After the fretting tests, the wear scars were deep, demonstrating a degraded anti-wear property, and fretting fatigue wear was dominant. The degradation of the fretting wear resistance in specimens PC2 and PC3 can be attributed to the absence of the protection of NiO in the tribolayer, the large grain size, and the weak plastic deformation accommodation ability. The underlying mechanism is the dissolution of Ni induced by pre-immersion corrosion in the LBE. The present work provides useful information on the fretting behaviour of heat-transfer tubes in nuclear power plants related to the LBE environment. • The dissolution of Ni element and the formation of oxide layer are main corrosion mechanisms in LBE. • The pre-immersion corrosion behaviour results in a larger wear loss in the fretting behaviour. • The effect of pre-immersion corrosion on fretting wear mechanisms are illustrated systematically. • This work guide for the protection of heat transfer tube in nuclear power plants. [ABSTRACT FROM AUTHOR]

The fretting behaviors of a metastable β titanium alloy with three kinds of microstructures were studied. Special attentions have been paid to the underlying wear mechanism mediated by fretting conditions and microstructural features. The wear volume is more sensitive to the stroke amplitude rather than the normal loading. The mixed abrasive-adhesive wear is dominated in all fretting samples. The microstructural features make a significant contribution to the difference in the wear resistance and subsurface microstructure stability. Due to a large difference in the grain size and the ability of plastic deformation in adjacent grains, the SM (single-phase microstructure) sample is more favorable to initiation and propagation of cracks. The DM (duplex microstructure) and BM (basketweave microstructure) samples, however, have a high resistance ability to fretting wear and subsurface microstructure stability. This can be attributed to the large amounts of the β/α interfaces and the dispersed orientation distribution of α precipitates. The present work offers valuable experimental data for the prediction of fatigue life after fretting. • The fretting behaviors are evidenced to connect with coupling effect of microstructural features and fretting conditions. • The fretting wear volume is more sensitive to the stroke amplitude rather than the normal loading. • The microstructural origins of fretting wear mechanisms are illustrated systematically. • Microstructure features dependence on the subsurface microstructure stability is revealed in detail. [ABSTRACT FROM AUTHOR]