Several surface preparation techniques are being used like grit blasting, HP water jet roughening as well as mechanical roughening for the preparation of Aluminum cylinder bore surfaces before a thermal spraying can be applied. However, in case of spray-repaired CI cast iron engine blocks the conventional mechanical roughening processes - using cutting inserts with small dovetail-undercut geometry - are not applicable due to the high hardness and high material toughness. Therefore such CI engine blocks are bored oversize in order to remove the bore wear damage and subsequently this rough-machined surface is coated by a NiAl-bond coating material in order to provide sufficient bond strength for the functional top coating material. In this paper it will be demonstrated that the 2-step spray-repair process can be replaced by a single-step process by using a new diamond-roll-roughening method. This process leads to significant higher bond strength values than the conventional process, including the bond coating material. PAT Adhesion test results as well as microstructural cross sections of coated cylinder bores will be presented. The principle of the roll-roughening process is outlined. In addition it will be shown that different mechanical roughening methods can be combined to obtain high bond strength values for spray-repaired aluminum blocks which require a higher coating thickness to compensate for the depth of the original mechanical bore activation.

In an effort to inhibit a climate change, the European Union has decided to reduce the CO 2 emissions by approx. 30% by year 2020, as compared to the level of emissions in year 1990’s. In general, traffic is responsible for 20% of all CO 2 emissions and 84% of those emissions result specifically from road traffic. In accordance with the present targets of the CO 2 emission reduction the automotive industry has to meet strict regulations. The strict emission goals can only be reached by weight reduction of the vehicle and by an improved efficiency of engine and drive train. Close to 50% of the friction losses in a combustion engine result from the interaction between the piston ring and the cylinder bore surface. Therefore the cylinder bores as well as the piston rings were coated with new, low-friction materials. The friction behaviour was characterized in linear reciprocating tribometer-test in order to identify the best combination of bore and ring coatings.

Hypoeutectic AlSi engine blocks of modern passenger cars are generally equipped with cast iron liners in order to provide cylinder running surfaces that meet the tribological requirements. A very promising alternative to the use of cylinder liners lies within the application of thermally sprayed coatings onto the walls of cylinder bores as friction partners for the piston rings. This work describes the development of a novel iron based wire feedstock as well as its application by the Plasma Transferred Wire Arc internal diameter coating system. The material developed within the frame of this work leads to partially amorphous coatings with embedded nanoscale precipitations if processed by thermal spraying. The coatings were applied onto the inner diameters of test liners made of Aluminium EN AW 6060 and onto cylinder bore walls of in-line 4 cylinder engines. All substrates were mechanically roughened in order to obtain high bond strengths of the sprayed coatings. The coatings microstructure was analysed by light optical microscopy, hardness measuring by transmission electron microscopy. Furthermore the oil storage capacities of the honed surfaces were determined.

Crank cases of modern car-engines are made in general of light metal alloys, mostly aluminium alloys. Due to the low hardness of these materials, the use of cylinder liners, in general made of grey cast iron is required. The use of cylinder liners also leads to several disadvantages, such as the increase of the engines weight. The aim of this work in the long term is to replace these cylinder liners with a thermally sprayed nano-structured composite coating, characterised by high hardness. Therefore in this study a coating process employing a plasma transferred wire arc unit and a cored wire are used.

The application of wear resistant coatings onto the wall of aluminium engine cylinder bores by thermal spray have seen much development over the last 10 years, with regards to both equipment design and also to the material system used. While the technology has been successful in allowing the implementation of aluminium engine blocks into mass production, there is still room for improvement. One area that can be improved is the preparation of the substrate material in order to allow a good adhesion of the thermal spray coating. Grit blasting, a traditional preparation technique, is undesirable for a mass production environment due to the risk of the assembly areas becoming contaminated with grit. Therefore, an alternative method has been sought that can offer a suitable bond strength without introducing potential risks in the manufacture line. In this study, NiAl bond coats were sprayed onto aluminium substrates using the Plasma Transferred Wire Arc (PTWA) coating system developed by Ford Motor Company. A variety of surface preparation techniques, including traditional and some more novel methods, were used and analysed with respect to bond strength, ease of application and cost.

The German Army is using the Sikorsky helicopter Typ CH-53 G in the marine version, this means that the tail with the rear rotor can be folded sidewise in order to safe space during storage. During flight the fuselage is locked by two gear racks that slide in the bore hole of an aluminium housing. Due to the high friction during the movement of the steel racks the inner bore surface is damaged of up to 1 mm depth. In this paper the repair of this inner surface of the bore by arc-wire spraying is described. A special gun extension was developed so that the narrow bore (diameter 48 mm; length 400 mm) can be repaired. Preliminary test results with various materials are presented. Paper text in German.

Sufficient electrical insulation must be ensured between the individual connection plates made of the ODS alloy in planar high-temperature fuel cells. In this paper, APS coatings and coating systems consisting of zirconium dioxide or zirconium dioxide/aluminum oxide are sprayed onto structured plates made of ODS-chromium alloy, qualified and implemented. The electrical insulation of both the coatings and the sealing glass composites is determined at 850 deg C and 950 deg C. The gas resistance of the coated sealing glass composite samples to air, hydrogen and hydrogen/water is determined experimentally. The coating technology is developed for small series production and successfully implemented on a large joined multi-cell unit with basic dimensions of 260 x 260 millimeter square. The paper demonstrates that this coating technology is sufficiently developed for industrial applications. Paper includes a German-language abstract.