Fabricating fluorosilane self-assembled molecular film on Babbitt alloy and its tribological performance

Purpose This study aims to improve the tribological performance of Babbitt alloy under oil lubricant condition. Thus, the surface was treated into oleophobic state by modifying with low surface energy fluorosilane (1H,1H,2H,2H-perfluorodecyltriethoxysilane). It is believed that the oleophobic surface offered excellent wear resistance of Babbitt-based tribo-pairs. Design/methodology/approach By modifying the Babbitt alloy with low surface energy fluorosilane and measuring the oil contact angle, the wetting behavior was evaluated. Using Pin on Disk tribometer, the tribological properties of bare Babbitt and modified Babbitt were quantified. The samples after the friction test were characterized by scanning electron microscope (SEM) and the anti-wear performance was evaluated under dry and oil lubrication conditions. Findings Results showed that oil contact angle of modified Babbitt was109° which was tripled compared to that of prime surface, which indicates the oleophobic behavior was greatly improved. Under dry conditions, the friction coefficient of the modified surface with different load conditions is slightly lower than that of the bare surface, while the friction coefficient of the modified surface under lubrication conditions is significantly decreased compared to that of the bare surface. Interestingly, under low load and high load, the wear rate of the modified Babbitt alloy surface is only 1/4 and 1/3 of that of the bare surface, respectively. Originality/value The work proposed an effective method to improve the Babbitt tribological performances and will lighten future ideas for the Babbitt alloy bearing with high wear resistance, which is beneficial to improve the service life of sliding bearings and has huge promotion and application value in the manufacture of sliding bearings.

Failure analysis of a bearing bush of a feed water pump

BACKGROUND: A rolling bearing bush alloy of a feed water pump that is part of a waste heat boiler of an oil refinery has failed. OBJECTIVE: We try to analyze the reasons that caused the working surface of the bearing bush of the water pump to fall off and then give some suggestions to this failure. METHODS: The composition, microstructure, pit, and crack morphology of the bearing bush alloy were analyzed by the X-ray fluorescent analysis, the energy spectrum analysis, the optical microscope and the scanning electron microscope, respectively. RESULTS: The content of Pb in the bearing bush alloy was high, and the Cu content was low. The primary crystal Cu6Sn5 was low, and the crystal of SnSb with low density moved upward and segregated. The above phenomenon reduced the fatigue resistance of the babbitt alloy. The bearing bush was subjected to alternating loads in service, and several small cracks were generated on the bearing bush alloy working surface. The cracks continued to expand and connected with each other. Fatigue pitting occurred on the bearing bush working surface, a large number of pits were formed, and several large alloy blocks fell off. CONCLUSIONS: The Pb content in the failed bearing bush alloy was too high and did not meet the requirements of the Sn-based babbitt alloys in the national standard. At the same time, the primary crystal Cu6Sn5 formed by Cu and Sn was low due to the low Cu content, and the crystal SnSb with a small density moved upward and segregated. The composition of the babbitt alloy, especially the Cu content, should be strictly controlled to ensure the safe and reliable operation of the bearing.

Tribological Performances of Modified Babbitt Alloy Under Different Sliding Modes

This paper aims to improve wear resistance of bare Babbitt modified by CuLa and evaluates the effect of different sliding modes on tribological properties of bare Babbitt, Babbitt modified by 0.5 wt% CuLa (marked by mbabbitt-1), and Babbitt modified by 1 wt% CuLa (marked by mbabbitt-2). First, bare Babbitt was modified with different contents of CuLa. The microstructure, microhardness, and wettability of Babbitt were tested and studied. Then, the tribological properties of bare Babbitt, mBabbitt-1, and mBabbitt-2 were conducted by the reciprocating mode and unidirectional mode under the lubricated condition. The results showed that the SnSb grain of the modified Babbitt was refined and uniformly distributed. The microhardness of mBabbitt-1 was higher than that of bare Babbitt and mBabbitt-2. Compared with bare Babbitt, the wettability of mBabbitt-1 and mBabbitt-2 was improved. Anti-friction and wear resistance of specimens under the reciprocating mode were better than that of specimens under the unidirectional mode, which was attributed to low strain and equivalent stress of bare Babbitt under the reciprocating mode. Moreover, anti-wear of bare Babbitt was improved by adding CuLa due to refined grain and high microhardness.

Interfacial Fracture Toughness Measurement of Welded Babbitt alloy SnSb11Cu6/ 20Steel

The interface fracture toughness of SnSb11Cu6/20steel was measured by calculating the critical energy release rate and stress phase angle of the interface crack. A three-point bending test was used to introduce cracks into the bonding interface, and the cohesion model of the bonding interface was established through experimental data. Through finite element analysis of load-deflection curves with and without interface crack propagation, the crack initiation point is found. Then the energy calculation model of crack propagation is established, and the critical energy release rate is obtained using the virtual crack growth criterion. The calculation results of the stress phase angle show that the crack propagation is greatly affected by the normal stress after the babbitt alloy layer fractures. If the strength of the substrate material is weaker, the crack will continue to expand in the tangent perpendicular to the crack tip.

Fabrication and Characterization of Sn-Based Babbitt Alloy Nanocomposite Reinforced with Al2O3 Nanoparticles/Carbon Steel Bimetallic Material

Sn-based Babbitt alloy was reinforced with alumina nanoparticles to prepare a novel class of nanocomposites. The route of liquid metallurgy in combination with stirring mechanism was chosen to prepare nanocomposites with three different loadings of alumina nanoparticles, i.e., 0.25 wt%, 0.50 wt% and 1.0 wt%. The molten mixture of metallic matrix and nanoparticles was poured over carbon steel substrate for solidification to manufacture a bimetallic material for bearing applications. The underlying aim was to understand the effect of nanoparticle addition on microstructural variation of Sn-based Babbitt alloy as well as bimetallic microstructural interface. The addition of 0.25 wt% and 0.50 wt% alumina nanoparticles significantly affected both the morphology and distribution of Cu6Sn5 hard phase in solid solution, which changed from needle and asterisk shape to spherical morphology. Nanocomposites containing up to 0.50 wt% nanoparticles showed more improvement in tensile strength than the one containing 1.0 wt% nanoparticles, due to nanoparticle-agglomeration and micro-cracks at the interface. The addition of 0.5 wt% nanoparticles significantly improved the wear resistance of Sn-based Babbitt alloy.