Abstract
The coating materials commonly used in hydrodynamic bearings are the so-called “Babbitt metals” or “white metals”, as defined by ASTM B23-00. Their low Young’s modulus and yield point have encouraged researchers to find new coatings to overcome these limitations. In this paper, the friction and wear of PEEK are studied in a dry sliding environment (without lubrication) using a ball-on-disk tribometer and compared to those of Babbitt metal. Furthermore, the bond strength tests between PEEK and metals/alloys are evaluated. PEEK polymer samples were obtained from cylindrical rods, manufactured by an innovative process for polymer bonding on bearing surfaces, using additive manufacturing technology. The morphologies of the degraded surfaces were examined using a high-resolution metallurgical optical microscope (OM) and a scanning electron microscope (SEM). The coefficients of friction (CoF) were obtained under the alternating ball-on-disk dry tribometer. The results of the experimental activity show that PEEK polymers have CoFs of about 0.22 and 0.16 under the 1 and 5 N applied load, respectively. The CoF and wear volume loss results are reported and compared to the reference Babbitt coating.
Highlights
Rotating machines, especially turbines, have had considerable technological evolution since their introduction
White metals do not have to be hard, but this means that they have a rather low Young’s modulus, as well as a low yield point that is about 45.5 MPa at 20 ◦C and decreases to almost half at 100 ◦C
In the present research work, the tribological performance of different PEEK-based polymer coatings, namely PEEK 101010 and PEEK cf15, were investigated using a ballon-disk machine in sliding mode at different loads at room temperature and compared with the Babbitt metal coating conventionally used in the bearing field
Summary
Especially turbines, have had considerable technological evolution since their introduction. Neglecting the historical testimonies that would trace their origin back to Heron of Alexandria from the first century BC [1], the modern steam turbine was invented in 1884 by Charles Parsons [2]. His patent was licensed and the turbine scaled by George Westinghouse. Not all the components that compose the rotating machines have undergone technological evolution; in particular, the materials used in bearings differ little from those used in pioneering applications, see for example [3]. White metals do not have to be hard, but this means that they have a rather low Young’s modulus, as well as a low yield point that is about 45.5 MPa at 20 ◦C and decreases to almost half at 100 ◦C
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