Vlastnosti kovo-keramického návaru s vloženými zrny karbidů wolframu

Abstract

Each machine part used in the industry during its service life wears out. Worn area is often small in comparison with the rest of the components which didn’t spend its lifetime in the whole profile. Hard-facing allows us to surface treatment of these components or their renovation. This adjustment method allows us to prolong the service life of extremely stressed parts. It is possible to increase the service life by using a suitable filler material with a higher strength Rm or using so-called composite materials such as tungsten carbide particles in a matrix of the weld deposit.

Currently there are a number of technologies that can be used for applying the special protective surface layers. This group of technologies includes thermal spraying, various coatings and also hard-facing. These protective layers are used in mining and metallurgical industry, construction, and for the parts subjected to wear, which is present in a form such as adhesion, corrosion, erosion and abrasion in particular, which significantly contributes to degradation of components used in these industries.

Such a protective layer can also include special weld deposits, using eg. the iron, aluminum, nickel or cobalt based matrix in combination with tungsten carbide particles with properties that belong to the group of the composite materials, which are slowly replacing the conventional components using tool steels. High hardness of the tungsten carbides along with the use of relatively tough matrix allows us to achieve high resistance to the different types of wear. This resistance significantly increases the service life of the machine components and significantly contributes to reduce the costs of industrial companies for repairs or replacement of these parts.

In the area of hard-facing, the manual metal arc welding can be used, plasma and laser, or receding flame surfacing. To one of the most progressive methods is hard-facing in protective gas atmosphere using the cored wires.

Dissertation thesis deals with hard-facing surfaces using the embedded particles of tungsten carbide in a martensitic matrix based on iron, in combination with the base material S235JR+N or S690QL. The main objectives of this work include studying the influence of welding parameters on embedded tungsten carbide particles in order to achieve a satisfactory weld deposits with the desired properties, particularly abrasion resistance. Weld deposits were subjected to the study of micro and macrostructure, chemical composition and assessment of the hardness measurements and the micro-hardness measurements. Part of this work was comparison of the amount of the tungsten carbide particles on the surface of the weld deposit and study of their impact on the service life of the final weld deposit. It was subsequently conducted an experiment to determine the resistance of welded deposits against abrasion and comparison of the used shielding gases and its influence to abrasion-resistance.