This paper presents the results of studies on powders used in wear-resistant thermal spray coatings. The work focuses on the influence of the shape, size, and structure of composite powders containing nickel, iron, and chromium mixed with TiC and dry lubricants such as MoS 2 and CaF 2 . The powders are analyzed using SEM and metallographic methods along with X-ray diffraction. Paper includes a German-language abstract.

In the present paper mathematical model of the deformation behavior of a liquid spherical particle upon its impingement onto a solid surface, including flattening and simultaneous solidification is developed. Particle-substrate interactions are investigated for typical thermal spray process. Numerical simulation for the complete Navier-Stokes equations is based on the finite-difference method on rectangular mesh in cylindrical coordinates. The energy equation is solved for both particle and substrate regions using the adjoint conditions for the temperature. In this paper main attention is paid to investigation of the temperature in contact of the particle with substrate. In connection with the oxide films effect on the surface substrate taking onto account thermal resistance of oxide is simulated. Heat transfer process in particle and substrate has been modeled by 2-D problem of heat conduction with influencing hydrodynamic processes into molten particle. Particle solidification and the movement of the solidification front have been described by means of one-dimensional Stefan problem. Numerical results for the heat transfer process and the effect of some important processing parameters such as particle diameter, viscosity, oxide films and temperature of plasma on the flattening and solidification of a single liquid particle have been discussed. Numerical algorithms were realized in the form of applied programs complex.

Conducted are investigations of powders for plasma spray of wear resistant coatings. Studied are shape, relief and particle size of NiCr-Fe+50(80)%Cr 3 C 2 , NiCr-Fe+50(80)%SiC powders using scanning electron microscopy. Investigations is supplemented by the results of X-ray structural studies. Investigations serve to develop coatings with the improved oil trap capability, increased hardness and wear resistance, sprayed by a plasma jet. The developed coatings will be used to restore and strengthen machines components

This article investigates composite powder materials based on double chromium and titanium carbides with nickel-chromium binder produced using self-propagating high-temperature synthesis. It focuses on the hypersonic velocity oxygen fuel coatings from the synthesized powders. Laboratory tests were focused on the solid particle erosion which occur in energy production systems such as fluidized bed combustors, advanced pulverized cool boilers, and entrained coal gasifiers. Tests were conducted at elevated temperature in a blast nozzle type of tester using bed or fly ashes retrieved from the operating CFB boilers. It was observed that, when adjusting carbide phase composition and chromium content in titanium carbide solid solution, one can control the oxidation kinetic and wear resistance of the material. Fine-grained structure and high cohesion strength of the composite materials formed during synthesis provide their excellent elevated temperature erosion performance in a wide range of test conditions.

Mathematical and computer models of movement and heating of particles in low pressure conditions are developed. The mathematical models are based on the molecular-kinetics theory of gases. A program complex for computer realization of models is developed. It contains a built-in data base of temperature dependent properties of substances, system of processing and graphic visualization of simulation results. For verification of the developed models, computer simulation and experimental measurements of Al2O3 particle temperature and velocity are conducted. These materials were sprayed with Plasma-Technik equipment at pressure 60 mBar in argon. Particle velocity was measured with a special optical device, particle temperature was defined by intensity radiation method. It was established that the developed models are adequate to real process (error of 5-8 %) and may be used for study and improvement of VPS processes.

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.

The following contribution deals with carbide composite powders. These composite powders were made by the SHS-process. The present work is a result of a co-operation between the Institute for Powder Metallurgy Minsk (PMI) and the Department of Composites and Surface Technology at the Chemnitz University of Technology (TUC). The main aspect of this research activity is the improvement of the wear protection due to the deposition of the composite coatings. Paper text in German.

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.

In this paper, the flattening and the simultaneous solidification of a liquid particle when it hits a solid surface are described mathematically and numerically simulated in cylindrical coordinates on the basis of the Navier-Stokes equations. The heat transfer in the particle and in the substrate is simulated by solving the 2-D heat conduction problem, whereby hydrodynamic processes in the melted particle as well as pressure forces are taken into account. The particle solidification is investigated using the one-dimensional Stefan problem, taking into account the contact heat conduction at the boundary between particle and substrate. For numerical calculations, computational algorithms were created on the basis of the difference method, which were implemented in the form of an applied program complex. Paper includes a German-language abstract.

Ti-implants plasma-sprayed with a hydroxyapatite (HA) coating are widely used. When using an implant the coating quality is characterized by the presence of HA decomposition products and sprayed material structure. This paper investigates the properties of hydroxyapatite coatings and their dependence on the types of plasma spray. The types of hydroxyapatite decomposition on titanium substrates using plasma spray technology are optimized. Paper includes a German-language abstract.

This paper investigates the wear resistance of NiCr-Fe+50(80)%chromium carbide and NiCr-Fe+50%SiC coatings. This is achieved by the plasma spraying of composite powders and the mechanical mixing of powders, followed by an additional treatment with pulses of a plasma jet. The mechanism of wear of the sprayed coatings is also analyzed. Paper includes a German-language abstract.

In this paper, a comprehensive mathematical model is developed for the integrated simulation of the coating plasma spraying process under low pressure. This simulation models powder particles that are heated and moved in a plasma jet, the heat transfer in the "coating substrate" system, and the formation of thermal loads. Basic software is developed for the practical implementation of the model. The process of alumina spraying is simulated. Paper includes a German-language abstract.

The melting of plasma-sprayed thermal barrier coatings (TBC) using highly concentrated energy sources is one of the methods associated with increasing the density of the sprayed material and modifying the phase composition in order to improve the properties of these coatings. This paper presents the results of the investigations into TBC melting using pulse and continuous carbon dioxide lasers. Paper includes a German-language abstract.

On the base of gases molecular and kinetic theory a mathematical model of interaction between powder particles and plasma jet is developed. Three-dimensional description of plasma forming gas density distribution as well as particle motion in the plasma jet are a characteristic property of the model. A software for practical realization of the mathematical model is created. Said software provides the possibility to investigate an effect of low-pressure plasma spraying parameters on particle velocity and coordinates in the plasma jet. Computer simulation of particle velocity for powders from aluminium and tungsten oxides in argon plasma under 60 Mbar is conducted. A "Plasma-Technik" VPS unit is used for testing the developed model. Particle velocity measurement is made by a specially developed optical-electronic unit.

This work evaluates the potential of using new competitive powders of Fe/TiC system for plasma spraying of wear resistant coatings. To improve coating properties, Cr and Ni were added to the iron matrix. The results of complex investigations of plasma coatings from such materials are presented.

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.