During the last decades, improved understanding of tribological behavior of different material combinations led also to an intensified development of thermal spray applications. In the field of e.g. hard chromium replacement by thermal spraying, significant amount of work has been done and published world wide, however, the authors manly focused on only one tribological aspect like friction, abrasion, erosion, cavitation or corrosion, respectively. In real applications, often more than one of those factors influence the successful use of these coatings. Besides the bulk properties of the materials, the coating micro structure, which is strongly spray system dependent, needs to be considered and investigated. Higher functionality and reliability than conventional competitive coatings still has to be proved at laboratory scale and under field conditions for thermally sprayed coatings. This paper describes the state of the art of thermally sprayed coatings as alternatives for other coatings. Published literature data and a wide range of own tribological investigations and field tests, reveals the potential for other applications.

Three iron-base alloys with different chemical compositions were developed and sprayed in these investigations. The effect of different process parameters (primarily a reactive APS and VPS process) on the attainable nitrogen concentrations and on the resulting coating structure is demonstrated. Furthermore, the metallurgical interaction between the selected alloys as a result of the spraying process is described and the properties (such as hardness, porosity and bond strength) are discussed. The objective of this development is to form nanostructured deposits of the vanadium-nitride type with a crystal structure similar to that of the austenitic lattice. The formation, appearance and type of deposits are described as functions of the process parameters. Paper text in German.

In the present project, the widest possible variety of coats applied by means of high-speed flame spraying are investigated with regard to their applicability to components of hydroelectric power stations. The investigations concentrate on protective coats for the wear surfaces of turbine wheels and various guide vanes. The structural shapes and specific features of different turbine wheels, forms of wear phenomena and their causes as well as experience with different materials and coatings are described. The resulting planning and stipulation of suitable testing conditions for the targeted investigations with high-speed flame- sprayed coats are also described. Paper text in German.

In thermal spraying, Fe-based alloys are often applied for relatively thick and inexpensive coatings. The main advantage of the Fe-based alloy coatings is their high ductility as compared to ceramic and hardmetal coatings. Other advantages such as high toughness, easy machineability and satisfactory corrosion resistance are characteristic of Fe-based alloys. The wear resistance is not outstanding, but nevertheless acceptable for a large number of applications. A further improvement of the wear resistance can be achieved by reinforcing the Fe-based alloy coatings, e.g. by addition of nitrogen to the spraying powder.