The use of diamond-impregnated tools for the machining of any type of building material or natural stone is an established technology. Sintering and brazing are the key manufacturing technologies. The restricted flexibility of the geometry variation, the absence of the repair possibilities of damaged tool surfaces as well as difficulties in controlling the materials interfaces are some drawbacks. Therefore, manufacturing diamond tools through new technology concepts are required not only to avoid these restrictions mentioned but also to enhance the tools properties. In particular, thermal spraying technologies can act as a potential problem solver due to their special technological properties. Especially the new high-speed technologies such as the detonation-gun and high velocity oxygen fuel thermal spraying are promising approaches. Through these technologies, it is possible to control the kinetic energies of the diamond particles as well as their temperature during coating. In this report, a novel manufacturing technology of the diamond-impregnated tools based on these high-speed thermal spraying technologies will be reported. The layer properties will be evaluated with respect to the diamond quality after coating and with respect to the properties of the diamond composite coatings. Diamond spraying efficiency, diamond distribution in the layer as well as diamond-metal binder-interaction are analysed.

Coatings of Metal-Matrix-Composite (MMC) with enhanced wear resistance were created by thermal spraying. The used powders composed of iron and nickel aluminides reinforced with alumina, Cr- and Ti-carbides were produced before by self-propagating high temperature synthesis (SHS). The fused and crushed composite powders were sprayed by atmosphere plasma spraying (APS) and gas detonation spraying (D-Gun). Spray powder and coating properties like morphology, structure, microhardness, porosity, bond strength, wear and corrosion resistance are examined using optical and scanning electron microscopy, XRD analysis, pin-on-disc (wear resistance). The produced MMC coatings are compared to commercially used wear resistant coatings, e.g. high velocity oxyfuel flame sprayed Cr 3 C 2 -NiCr. The properties of a special coating type depend on the used spraying method. Plasma sprayed MMCs show a slightly higher porosity than D-Gun sprayed coatings. The chemical composition of used powders has a big influence on the coating properties. Fe- and Ni-aluminide matrix coatings reinforced additionally with carbides, especially Cr 3 C 2 , show a better wear resistance compared to coatings containing just oxides as hard material.

In this paper, metal matrix composite layers are produced by thermal spraying using cored aluminum wire. Two types of wire were produced, one containing mechanically alloyed Al and Cr 2 O 3 powders, the other, Al and AI 2 O 3 . The powders undergo self-propagating high temperature synthesis during the spraying process, which has a positive effect on coating properties such as bonding, cohesion, and wear resistance. Different spraying methods were used in the experiments, but satisfactory results were only achieved via atmospheric plasma spraying. Paper text in German.

This paper shows how thermal spraying, with an additional thermal treatment, can be used to join metal parts and fill surface defects. The joining and surface repair methods demonstrated in this work involve a wide range of materials and processes, and the results are characterized based on microstructural and elemental analysis and various property measurements. Paper text in German.

This study investigates the influence of plasma gas composition on deposition efficiency achieved during atmospheric plasma spraying and the properties of the resulting deposits. In the experiments, ternary mixtures of argon, hydrogen, and helium are used in different combinations and flow rates to spray Al 2 O 3 -TiO 2 and ZrO 2 -Y 2 O 3 powders on test substrates while measuring deposition efficiency. Several coating properties are measured, including porosity, hardness, and bond strength, and correlated with plasma gas ratios. Paper text in German.

The properties of thermal sprayed coatings depend mainly on the thermal and kinetic energy of the spray particles. Increase of thermal energy of sprayed particles can be realized using exothermic reactions between components in sprayed particles. Self propagating high temperature synthesis (SHS) is especially suitable to benefit from released energy in the spraying process. At present most commonly used spray material with exothermal reaction is Ni+Al. However, the highest amount of heat is produced in the reactions of aluminium and metal oxides. Of special interest are Cr 2 O 3 , NiO, CuO and V 2 O 5 because they obtain high reaction energies. Furthermore products of the reaction are of special, functional interest like NiAl as bonding agent or alumina as a wear resistant coating. To assure good contact between reacting substances (Al/Oxides) powders for plasma spraying were prepared by mechanical alloying. Calorimetric investigations of plasma sprayed coatings prove that during spraying Al reacts exothermically with oxides. Increase of oxide contents improves coating adhesion/ cohesion properties, hardness, and reduction of porosity. Results are discussed on the base of light microscopy, scanning electron microscopy (SEM) and X-ray structure analysis (XRD).

TiN reinforced Ti coatings were produced by using the arc spraying process. TiN hard phases were synthesized during spraying using Ar/N 2 reactive atomizing gas. The spray process was realised in an air atmosphere with a shrouded gun and in a chamber with closed loop Ar/N 2 -gas atmosphere. The content of TiN phases in Ti-coatings was increased by rising the N 2 -amount in atomizing gas during spraying. Sprayed coatings obtained a graded hardness ranging from 450HV 0.1 near the substrate up to 650HV 0.1 near the top (mean values). TiN-particle precipitations exhibited micro hardness up to 1350HV 0.1 . Structure investigations of manufactured coatings proved that they consist of pure titanium, titanium nitrides and small amounts of titanium oxides. Wear resistance of the coatings, tested by Taber Abraser and Pin on Disc, decreases from the coating surface to the substrate. According to Kesternich test, Ti/TiN-arc sprayed coatings exhibit good corrosion resistance.

Aluminum coatings reinforced with either Al 2 O 3 or SiC particles were deposited onto aluminum substrates and subjected to various tests. The coatings were made with mechanically alloyed powders via atmospheric plasma spraying (APS). Both types of coatings had uniformly distributed hard particles, porosities in the range of 4 to 5%, and bond strengths of around 20 MPa. The wear resistance of the SiC-reinforced coatings, however, was almost 35% higher than the coatings containing Al 2 O 3 . X-ray examination (XRD) showed that the Al 2 O 3 particles undergo partial phase transformation during spraying, making them more prone to wear.

Wire flame sprayed molybdenum is a wide used procedure for manufacturing of wear resistance coatings. The properties of thermal sprayed coatings depend mainly on the kinetic and thermal energy of sprayed particles, i.e., a higher particle velocity causes an increase of coating quality. The now available high velocity spray system from Praxair which is used within this work is capable to realise the aim of high particle velocities. The coating properties presented in this work are analysed in comparison to conventional wire and powder plasma spray processes. HVWFS molybdenum coatings show lower porosity, higher adhesion and cohesion and better wear properties. To explain the results, particle size distribution, oxygen/carbon content and structure are analysed. Hardening mechanisms of coatings and their adhesion/cohesion properties are discussed based on light microscopy, SEM, XRD and TEM investigations.

For obtaining higher particle velocities and consequently dense coatings, a closed nozzle system for atmospheric arc spraying was developed. The proposed system is characterized by a nozzle geometry which allows an expansion of the atomizing gas only in downstream direction. First coatings, obtained with this system exhibited promising results due to dense structure and high adhesion. Paper text in German.

This paper examines thermal insulation layer systems with regard to their thermal shock resistance, internal stresses, adhesive tensile strength and layer morphology. The research was conducted on a duplex coatings system consisting of zirconium dioxide/yttrium oxide ceramic coatings and CoNiCrAlY oxidizing and corrosion resisting coating. In all thermal insulation layer systems, the bonding layers were produced by vacuum plasma spraying. The thermal insulation layers were produced on the one hand by atmospheric plasma spraying and on the other hand by vacuum plasma spraying, and their properties were compared with one another. Paper includes a German-language abstract.