Molten metals are extremely corrosive against steel-made molds. In addition to alternating thermal loads and erosion by hard particles the lifetime of molds in the permanent-mold casting industry is rather short. Tungsten-based pseudoalloys are able to increase the lifetime of these molds significantly, but, by now, their use is limited to sintered inlays at the mostly stressed parts of the mold. Coating the whole mold with these materials offers an increase of the lifetime and at the same time a reduction of the amount of deployed feedstock. Within this research project it was possible to increase the lifetime of a kernel in used in casting brass by a factor of 20 by cladding it with tungsten-based pseudoalloys. The metallurgical behaviour of the tungsten-based pseudoalloys is quite complex. By modifying the coating process different shapes and amounts of tungsten precipitations in the nickel-iron-binder can be realized. The different microstructure within the coating does strongly affect the mechanical and anti-corrosion properties of the coating.

Conventional processes of gas shielded metal arc welding (GMAW) do not offer directly the possibility for cladding heat sensitive materials such as aluminum with iron-based materials due to intermetallic Al/Fe phases form. This paper deals with the first evaluated cladding results of aluminum components with iron-based nanocrystalline solidifying materials by controlled shielded metal arc welding processes to improve wear resistance. In the present work, the design of experiments and data evaluations are systematically applied to get the first results about the dependence between controlled arc welding process parameters and the iron-based coatings of aluminum substrate. In particular, the effect of the chosen parameters such as wire feed speed, welding speed, frequency and further factors on the heat input, welding penetration, micro hardness, rate of welding penetration and width of intermetallic phases in the interface zone are investigated. Optical and scanning electron spectroscopy provide input for further statistical evaluation. The experiments were carried out using various controlled arc technologies which offer different control over the heat input to the substrates. Different power supplies were used.

The lifetime of casting molds in the aluminum industry is strongly limited by the corrosiveness of aluminum melts and alternating thermal and mechanical loads. With the added protection of sintered tungsten pseudoalloy inlays, casting molds have been known to last as much as 1000 times longer, and the work presented here indicates that it may be possible to replace the massive liners with a twin wire arc or plasma sprayed coating that can be tailored by varying spraying parameters.

The aim of this investigation is to show that it is possible to inject powder into a wire arc spray process as an alternative to using cored wire to produce particle-reinforced coatings. The equipment, materials, and procedures used are described in the paper along with the microstructure and properties of the coatings obtained. By changing the feedrate of CrC particles injected into a stream of chromium steel droplets, particle-reinforced graded layers were produced by wire arc spraying on the fly without having to stop the process.

Due to its easy handling and low operating costs, wire arc spraying has become one of the most established processes for applying protective coatings to components used in waste incineration plants. This paper discusses the development of relatively low-cost Fe-Cr-Si coating materials for incinerator applications and the corrosion and wear properties that have been achieved using conventional arc spraying methods.

This work investigates some of the unique properties that can be achieved by combining materials with positive and negative thermal expansion coefficients. In the experiments, different mixtures of MCrAlY, WO 3 , and Y 2 O 3 powders are deposited on stainless steel substrates by laser cladding and HVOF spraying. To facilitate the formation of negative expansion coefficient particles in a positive expansion coefficient matrix, nucleation centers are created by ion implantation followed by heat treating. SEM examination and XRD analysis of the coatings obtained confirm the viability of the processing approach.

Casting molds in the aluminium industry show a short lifespan due to the high corrosiveness of aluminium melts and alternating thermal and mechanical loads. By using new materials, in example pseudoalloys containing tungsten, the lifetime of casting molds can be elongated up to hundredfold. Today, casting molds made of steel are state of the art. In spite of the advantages of pseudoalloys, high manufacturing cost and the increasing commodity price of tungsten prohibit the use of molds consisting of these progressive materials. By coating the standard steel molds with a FeNiW-layer, the excellent thermal and corrosive resistance of the pseudoalloy surface can be combined with minimal manufacturing costs. For present work steel substrates had been coated with FeNiW-pseudoalloys. Therefore, arc spraying and different deposit-welding methods (Laser, Plasma, TIG) had been compared. By modifying the machine parameter set, a smooth transition between substrate and coating was realized. Thermal and chemical resistance of the samples will be tested. In this paper first results are presented.

Increasing requirements on technical components for high-temperature-applications (e.g., turbine blades) demand for new developments in surface engineering. The selective combination of materials with positive and negative thermal expansion coefficients (NTE) will lead to a reversible activation of the surface depending on surface temperature: The generation of a riblet structure (“shark skin”) in operation condition by thermal expansion of the matrix and shrinkage of the NTE-ceramic and self-cleaning of the surface at cool down as a result of the reversal of the process. Due to its hygroscopicity the chosen NTE-ceramic Y 2 W 3 O 12 needs to be embedded into a binder matrix. Therefore a feedstock powder consisting of MCrAlY, WO 3 and Y 2 O 3 is mechanically alloyed in a high-energy ball mill. The powder is deposited on substrates by thermal spraying (VPS and HVOF) and laser cladding as well. After coating process a lateral- and depth-selective ion implantation of tungsten, yttrium and oxygen will force nucleation in predefined areas. A following heat treatment of the specimens supports the in-situ-formation of Y 2 W 3 O 12 .