Особливості дослідження міцності зчеплення композиційних контактних матеріалів зі зношеними деталями електрообладнання

Анотація

FEATURES OF RESEARCH OF GRIP STRENGTH COMPOSITE MATERIALS CONTACT WITH ELECTRICAL worn parts

I. Radko, M. Marhon

Now the problem is urgent restoration of contact nodes switching devices. Methods of recovery are different. After spraying contact materials necessary to conduct studies on adhesion contact materials with worn parts of electrical equipment.

The purpose of research - set adhesion contact materials with worn contact details nodes.

Materials and methods of research. To determine the strength of adhesion with the base contact materials in restoring contacts necessary to determine the hardness fatiguability and permeability.

Results. Hardness is measured impedance of that one body makes it more penetration, more solid. This characteristic reflects a range of mechanical properties. Tests on the hardness of the material with coatings performed for quality control applied layer, detecting changes in the surface areas of the base metal, to assess the structural heterogeneity in section coating in order to study patterns of wear surfaces, determining the strength of the connection with the base metal coating and so on.

There are standards governing the measurement of hardness. The standard defines the parameters and limits of permissible error stationary hardness produced by domestic industry.

The method of microhardness are micro hardness of the coating. The main purpose of the method - the study of the hardness of individual particles, structural components and anisotropy of hardness in different parts of the coverage. There are two methods of testing: the restored print (basic method) and the unreduced fingerprint (optional method). Result for the first test method describes the resistance of the material of plastic and elastic deformation during pressing a diamond tip static load for a specified time. After removing the load and remove the tip of measured parameters print, the remainder of which, taking advantage of formulas and tables determine the value of micro hardness.

Samples for micro hardness measurements are metallographic gr.

The disadvantages of micro hardness measurement method should include a high level of uncertainty, especially increasing the study of surfaces using small loads.

The term "fatigue" is meant a process of gradual accumulation of damage to the material under the alternating voltage, which leads to changes in the properties, formation and development of cracks and decay.

According to research samples of coatings can be fatigue, dusting off technology covered; select the optimum combination of chemical composition, structure and properties of materials and cover the base metal; calculate and project design; conduct intermediate and output quality control composition "cover - base metal"; monitor critical parts with coatings before operating.

Microscopic examination of thin sections cross that cut the zones of destruction tired, found a large number of cracks perpendicular to the cover with the base metal. Usually the cracks run through share and stop at the border that separates the particles. This feature is typical for brittle coatings and for plastics.

Research planar contact with coatings carried on combined experimental plants, to determine the fatigue limit, build curves small cycle fatigue, observe the origin of the cracks in the coating of pre-established hub voltage to determine the kinetics of spreading cracks in the coating and base metal.

Sprayed metal has a low ductility and impact resistant, and therefore the fracture surfaces is the formation of brittle fracture.

Despite the low mechanical properties of sprayed coatings, their joint strength at work enough to stand the restored contacts switching resource of 300 thousand. Switching cycles.

Permeability - the ability to pass through the material itself liquids and gases. Especially important to know the permeability of protective coatings that operate in hostile environments at high temperatures.

Numerical criteria permeability is permeability coefficients and filtering. Permeability increases with increasing porosity and depends on the voltage difference in the sample thickness and anisotropy coverage.

Of course there is a good correlation between porosity and permeability values. This can be used to detect cracks coverage. In the analysis of plasma and oxide coating was found that the gas permeability on the order of or greater than the value of their open porosity. As a result of microscopic studies covering fixed presence of microcracks that are increasing dramatically increase the porosity of gas permeability. Permeability coatings obtained by different methods may vary by five orders of magnitude, but even the most durable coating will not has plasma corrosion protection in particularly aggressive environments.

Conclusions

Conducting research restore contact assemblies allow the following conclusions:

- Getting local coverage of various contact materials are characterized by high strength and electrical resistance.

- Hardness material coated constant fatigue and suggest that restoring contacts withstand switching traffic to 300,000 switching cycles. The duration of the electric vehicle continues. Increased economic efficiency.