The aim of this work is to determine how to control the microstructure and tribological properties of HVOF-sprayed TiC composite coatings. The powders used in the study were made by the SHS process and contained a mixture of TiC and either FeCr20Ni10 or FeCr18Ni15Mo3, which serve as a binder and give the sprayed coatings additional corrosion resistance. The composites produced were assessed based on metallographic examination and wear testing. The results show how the structure of the SHS powder changes due to the injection molding process and how the tribological properties of the HVOF layers are influenced by spraying conditions and the formation of mixed carbides. Paper text in German.

Due to their attractive combination of properties (high resistance to oxidation and wear, high melting point, and lower density) iron and nickel aluminides show promise for the development of advanced materials and coatings However, poor room temperature ductility and susceptibility to intergranular cracking restrict their commercial application. To provide the structure required composite materials produced by the self-propagating high-temperature synthesis (SHS) are promising. In this paper, the potential of thermally sprayed NiAl/aluminum oxide and FeAl/aluminum oxide composite powders produced using the SHS method is evaluated. The results of the structure and property investigations for the synthesized powders as well as for the resulting plasma coatings are presented. Paper includes a German-language abstract.

Forming technology of protective properties using concentrated energy flows is based on the possibility of laser radiation firstly to provide high heat flow densities which are necessary for intensive heating on a small part of surface. When effecting metal surface laser radiation reflects from it partially and the rest flow penetrates on small depth. As far as the energy is practically absorbed fully in the surface layer, width 10 -6 to 10 -7 m, the heat source may be considered as surface one [1]. To harden steel products it is necessary to heat the surface till the temperature of phase transformations. The surface cooling takes place mainly due to heat transfer to a less heated member part. Mathematical modeling thermal processes occuring when local surface parts processing is one of effective means to study this method of materials hardering. However till now the predominant number of works of temperature fields investigation when local processing was done supposing that the ray effects semi-infinite space or the process is considered in a moving coordinates system, connected with the centre of a light spot, that enables to consider a stationary task. Such assumption are true when processing massive parts but give a considerable error when processing small parts [2]. The offered models with the aid of which there is studied the heating process for a sample of parallepiped and cylinder shape come to solving the equation of thermal conductivity with considerably nonlinear coefficients. When surface processing with continuity laser, the ray is focused perpendicularly to the sample surface. The period of light spot contact with the surface is estimated from the speed of its travel on the scanned surface. Before the test the product is subjected to special processing reducing the energy loss due to reflection.

This paper presents a mathematical model of the plasma-spray coating formation process that allows one to estimate bond strength energy, a parameter related to coating quality. Bond strength energy is defined on the basis of particle-substrate or system balance. Unknown quantities in the energy equation are obtained from nonstationary Navier-Stokes equations for velocity field and pressure and from thermoelasticity equations for temperature and stress. Complexities associated with particle spreading and nonlinear hydrodynamics have made it necessary to develop a stable numerical technique.