There are constantly increasing requirements concerning light-weight concepts in automotive design due to energy saving demands. Additionally reduction of component weight is desired for demountable parts to permit easier handling. One innovative development example in this field is a draw bar consisting of precipitation hardened aluminum featuring significant weight reduction compared to presently applied steel draw bars. However, low wear resistance of aluminum alloys makes sophisticated addition of wear resistant parts in the area of the positive fit necessary. This leads to increased machining time, further costs for purchasing and machining of adapted additional components and further assembling steps. A study on the capability of thermal spray coating deposition in the positive fit area for substitution of the sophisticated wear protection system is carried out. Different HVOF coating systems with variable thicknesses are tested concerning their capability to withstand bending stress. The optimum combination of Ni20Cr bond coats and Cr 3 C 2 - 25 Ni20Cr top coats is applied for prototype production. The prototypes are tested concerning their performance under dynamical load and in corrosion tests. All produced prototypes pass both mechanical and corrosion tests. Prototypes, on which arc-sprayed Ni20Cr coatings are deposited as a low-cost solution, are still in tests.

In order to overcome the disadvantage of local carburizing of steel components in contact with light-weight graphite or carbon fiber reinforced ceramic racks alumina based thermal spray coatings are produced as diffusion barriers with improved life time compared to rapidly degrading alumina or boron nitride pastes. The powder flame sprayed coatings are also capable to prevent damage by excess filler material in high temperature brazing processes effectively. Besides graphite also C/C racks are coated with pure alumina, Al 2 O 3 -TiO 2 and Al 2 O 3 -Cr 2 O 3 . Conventional powder flame spraying is applied in order to provide a low-cost solution for realization of diffusion barriers. Coatings are characterized by means of optical microscopy and SEM with regard to the interface to the substrates and their porosity. Coated racks are used in field tests for case hardening of steel components. The life time of thermal spray coatings is compared to alumina and boron nitride based pastes. Comparative liquid metal corrosion tests are carried out with NiCr7Si4.5B3.1Fe3 filler at 1,050 °C.

HVOF sprayed WC/Co(Cr) and Cr 3 C 2 /Ni20Cr composite coatings have gained high acceptance in many industrial applications for protection of components against wear. The achieved coatings have quite good corrosion resistance for use of chromium containing matrices. Present research in the field of PTA-Surfacing resulted in the development of high chromium and high vanadium containing iron based hard alloys with simultaneous improvement of abrasive wear and corrosion resistance. These properties of the PTA-Surfaced coatings were studied and it was found that the newly developed alloys have nearly same wear resistance and improved corrosion resistance compared to Co-based alloys reinforced with Fused Tungsten Carbides (FTC). One major advantage of high chromium and high vanadium containing iron based coatings is machinability by turning and milling processes. These features make it attractive to be used in thermal spraying. The absence of substrate melting in HVOF-spraying is advantageous, as the coatings preserve the properties of the alloy due to prevention of dilution with substrate material in contrast to PTA-Surfacing. High chromium and high vanadium containing iron based atomized powder was used for HVOF spraying and deposition efficiency was measured. The sprayed coatings were studied metallographically by optical microscopy, SEM, XRD and micro-hardness measurements. Later, abrasive wear and corrosion properties of the coatings are investigated.

This paper discusses the development of silicon carbide (SiC) composite powders for HVOF spraying. It describes the material properties of various carbides, examines the morphology of SiC powders, and presents the HVOF parameters typically used to spray SiC composite coatings. It also examines the microstructure and composition of SiC nickel and cobalt-base composite coatings and investigates their corrosion and wear behaviors. Paper includes a German-language abstract.

This study assesses the wear performance of HVOF-sprayed nanostructured TiB 2 composite coatings and the use of mechanical alloying for powder preparation. In order to prevent the formation of undesired secondary borides, TiB 2 particles are processed with a nickel-base self-fluxing matrix alloy. XRD analysis shows that the minimum average TiB 2 crystal size is 22 nm after high-energy milling and only slightly larger and uniformly distributed after HVOF spraying. The resulting TiB 2 layers are characterized based on morphology and wear behavior and are shown to hold promise for abrasive wear applications. Paper includes a German-language abstract.

This paper describes how mechanically alloyed SiC composite powders with different metallic matrices are produced and applied by HVOF spraying. The sprayed layers are characterized in terms of layer morphology and wear behavior and compared with conventional cermets. Paper includes a German-language abstract.

This work investigates the use of thermal spray molding in the production of microscale components with large aspect ratios. It evaluates a number of spraying processes and coating materials and discusses the impact of the base material on process control and product properties. It also demonstrates the use of simulation for determining optimal process conditions. Paper includes a German-language abstract.

This study examines the melting characteristics of wire feedstock used in arc and flame spray processes and how they relate to coating quality. A high-speed CCD camera reveals important details in how different types of wire melt away during spraying. Solid and tube cored wires, for example, melt off in a much more continuous manner than grooved wires during high-velocity combustion spraying. During arc spraying, however, no significant differences are observed. The paper also analyzes various coating microstructures and explains how they correlate with the melt off behavior of different wire designs. Paper includes a German-language abstract.

The main application of HVOF processes is the production of wear and/or corrosion protective coatings based on cermets (e.g. WC-Co). To reduce the weight of the sprayed volume, to increase the oxidation resistance and to reduce the costs of consumables SiC based cermets are of particular interest. The outstanding mechanical, thermal and chemical properties of SiC have made this material attractive for thermal spray applications. Thermal spraying of pure SiC is impossible, because of its decomposition at elevated temperatures. The development of suitable alloys as metallic binders enables the wetting of the SiC particles with reduced reactivity between the matrix and the hard particle during the thermal spray process. In the present work starting from the metallurgical concept of the metallic matrix to the production route from the atomization of the metallic matrices, the spray drying and sintering as well as the processability of the composites is discussed. The coatings are characterized concerning porosity and SiC content using optical and scanning electron microscopy, digital image analysis, X-ray diffraction and micro hardness testing. The wear resistance of the coatings is determined by oscillating wear test. Microstructure and performance of the SiC composite coatings are discussed with respect to technical applications.

High Velocity Oxygen Fuel (HVOF) spraying established itself as an effective method in addition to the conventional thermal spray processes within a very short period. Self fluxing nickel alloys, cermets (e.g. WC-Co / Cr3C2-NiCr) as well as oxide ceramic coatings have proved themselves suitable for wear protection applications. Weight reduction, the care of resources and the increase of efficiency for structural components leads to the substitution of customary hard particles. Titanium carbide (TiC) characterizes itself on account of the material features such as the high hardness, the high melting point, the high strength and the low density for the substitution of conventional carbides. The Self Propagating High Temperature Synthesis (SHS) is a suitable process for the production of composite powders. The powders produced by SHS show a high carbide content, which is finely distributed with an almost stoichiometric composition of the TiC inside the powder particles. The carbides are protected against dissociation and oxidation during the thermal spray process by a complete velum of matrix alloy. The current investigations deal with the wear resistance of TiC-composite coatings produced by HVOF compared to conventional wear resistant coatings. The investigations contain the analysis of the microstructure by optical and scanning electron microscope (SEM) and the measurement of the microhardness of the deposited coatings. Special attention is drawn to the interface between the hard particles and the matrix alloy. The optimized coatings are tested with different wear tests, such as Taber-Abraser test, sliding and oscillating wear test and are compared with common wear resistant coatings in order to underline the high potential for different wear applications. Moreover an additional corrosion test (salt fog test) is carried out with regard to the corrosion resistance of the different matrix alloys.

Thermal spraying of composite materials is an effective method for surface protection against wear and corrosive attacks. There are different possibilities to produce composite-materials for thermal spray applications. The self-propagating-high- temperature-synthesis (SHS) is a very promising method to obtain fine carbide particles homogeneously distributed in a metal matrix. In the present investigation TiC-based composite materials were applied to steel substrate samples by thermal spraying. The coating characteristics were determined by the use of different investigation methods. The results of the wear test show the great potential for industrial application. Further progress is expected from the optimisation of the thermal spray processes and the compounds composition. Paper includes a German-language abstract.

Laser shock processing (LSP) is a surface treatment similar to shot peening, in which the compressive stresses in the material are created by laser-induced mechanical impacts. The tensions are of sufficient intensity to modify the microstructure and properties. In this paper, the laser pulses are generated with a power density of 5 to 8 GW/centimetres square with a neodymium laser. The glass laser is used to treat Al+SiC composite coatings, which were initially applied using the high-speed oxygen fuel spray technique. The laser-processed samples are prepared metallographically and examined for their microstructure with a scanning electron microscope. The latter is also used to investigate the surface morphology of laser-treated samples. Finally, the microhardness and the vibration wear resistance of the coatings are tested and compared with the data obtained for the samples in the sprayed state. Paper includes a German-language abstract.

Oxide-bonded silicon nitride (OBSN) powders have been developed to address thermal spray problems associated with high temperatures. This paper examines how such powders perform when applied via detonation gun (DGS) and atmospheric plasma spraying (APS) with axial powder injection. All coatings were characterized using optical microscopy and X-ray diffraction with additional tests being performed on DGS coatings. For the first time, relatively dense Si3N4-rich coatings with an oxide binder phase were produced, and some of the DGS coatings were found to be sufficiently wear resistance for industrial use.