In state-of-the-art manufacturing of sliding bearings, brass components are soldered to respective parts, which is costly and energy-intensive. Furthermore, up to now most bearings still contain lead, which by EU regulations for new part has to be omitted due to associated health risks. Cold spraying can be employed as additive manufacturing technique and opens the perspective to deposit the requested bearings in desired leadfree layout where needed. Aside cohesion and tribological behaviour, sufficient adhesion of the coating is essential for applications. The present study aims to systematically elucidate the influence of surface roughness on adhesion. The surface roughness was adjusted by varying the grit blasting material, grit size, blast pressure, blast distance and substrate material with the aim to study influences by impact conditions, surface topography on particle deformation and bonding in cold spraying. The results show that the adhesion strength reaches a maximum for a certain roughness. The ideal surface roughness to ensure good adhesion of cold-sprayed coatings apparently depends on specific impact conditions related to the powder material strength but also on the substrate material strength and particle size distribution. By systematic tuning of blasting conditions, coating adhesion can be increased by about a factor of two, thus meeting the requirements for new lead-free bearings.

At present, main bearings in wind turbines are equipped with rolling bearings without exception. Sliding bearings instead can offer a number of advantages, including easier maintenance and extended lifetime. While conventional manufacturing processes for large sliding bearings face their limits regarding processable materials, thermal spraying can provide an effective alternative to meet the requirements by applying coating systems on the bearing surfaces. Within this study a wide range of different feedstock materials based on standard bearing materials and common wear and friction reducing coating systems are investigated. The coatings are tested on tribometers based on the load distribution within the main bearing at critical operating conditions of the wind turbine gained from a validated simulation model. A tribological methodology is developed to investigate the application related properties of the thermally sprayed coatings. The effects of load and geometry of the counter body on the friction and wear behavior of the coatings are investigated using a pin-on-disc and a modified high-load ring-on-disc tribometer. The presented results provide a major contribution to the purpose of identifying an appropriate coating system to meet the requirements of slow-moving and highly loaded sliding bearings.

Al-Sn plain bearings for automotive applications traditionally comprise a multilayer structure. Conventionally, bearing manufacturing involves casting the Al-Sn alloy and roll¬bonding to a steel backing strip. Recently, high velocity oxy- fuel thermal spraying has been employed as a novel alternative manufacturing route. The present project extends previous work on ternary Al-Sn- Cu alloys to quaternary systems, which contain specific additions for potentially enhanced properties. Two alloys were studied in detail, namely Al-20wt.%Sn-lwt.%Cu-2wt.%Ni and Al-20wt.%Sn-lwt.%Cu-7wt.%Si. This paper will describe the microstructural evolution of these alloys following HVOF spraying onto steel substrates and subsequent heat treatment. Microstructures of powders and coatings were investigated by scanning electron microscopy and phases identified by X-ray diffraction. Coating microhardnesses were determined in both as-sprayed and heat treated conditions and differences related to the microstructures which developed. Finally, the wear behaviour of the sprayed and heat treated coatings in hot engine oil was measured using an industry standard test and compared with that of conventionally manufactured Al-Sn bearings.

Aluminium-based plain bearings for gasoline internal combustion engines are traditionally manufactured by casting and rolling, followed by forming and boring. The application places severe demands on the bearing material and a combination of properties such as fatigue, seizure and wear resistance are required. These properties are achieved by using a multi-phase material comprising of a distribution of tin in an aluminium alloy matrix. HVOF has been investigated as an alternative process for bearing manufacture and as a route to producing novel bearing materials with microstructures that cannot be achieved using the conventional casting route. The work reported describes the use of different HVOF spraying systems and powder types to develop aluminium-tin based coatings for advanced bearing applications. The coatings are described in terms of microstructure characteristics. The fatigue performance of the advanced sprayed bearings is compared with conventional cast bearings.

In the present paper rheological behavior of the Oxide Aluminum-Polymer Composite Sliding Bearing was examined. The requirements to the rheological models were formulated regarding adequate strain-strain state of the bearing. Rheological models of the composite sliding bearing have been proposed and were confirmed by in-situ experiments using principal Hertzian theory as the background. Load rating tests have revealed ultimate stresses of the sliding bearing and the strain-deformation modes of the sliding bearing ’ elements. The Oxide Aluminum-Polymer Composite Sliding Bearing was presented in the form of the complex elastic-tenacious-plastic rheological model. The metal-polymer layer was modeled by the rheological model consisted from two elastic elements and one tenacious element. As a prototype of the model, we studied a model comprising the Maxwells’ model and an elastic element. In general, a rheological equation depends on a level and form of strain applied. Analysis of the models and experimental results revealed better understanding of nanocomposite fracture and degradation mechanics. The nanocomposite exhibits linear relation of strain curve, whereas unloaded composite shows retardation of deformations (elastic return). The relations of experimental data and calculated data revealed very close agreement of developed rheological model and real mechanical behavior of the nanocomposite.

This paper compares the corrosion, friction, and wear properties of thermally sprayed aluminum bronze coatings developed for use on plain bearing surfaces. It explains how the coatings were produced, characterized, and optimized for the intended application. Paper text in German.