Specific Features of Structure Formation in the Course of Modification of the Coatings on Products Made of Dispersion-Ha
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SPECIFIC FEATURES OF STRUCTURE FORMATION IN THE COURSE OF MODIFICATION OF THE COATINGS ON PRODUCTS MADE OF DISPERSION-HARDENED STEELS Т. S. Skoblo,1 A. I. Sidashenko,1 S. P. Romanyuk,1, 2 A. А. Goncharenko,1 L. V. Омеl’chenko,1 and V. А. Bantkovskii1
UDC 621.791.927
We analyze the technology of hardening and restoration of products made of dispersion-hardened steels and steels containing large amounts of nonmetallic inclusions. For the formation of coatings, we used secondary raw materials obtained as a result of the utilization of a certain collection of ammunition, including nano- and dispersed diamonds. We also study the influence of parameters of the technology of detonation charge modification in the process of surfacing on the metal structure of the restored product. The best results were obtained as a result of introduction of 5.0–7.0% of charge (relative to the mass of the electrode). This guarantees the formation of a homogeneous structure with grains of similar sizes in the coating and increases the wear resistance of the restored product by 25% and of the mating product by up to 37%. Keywords: coating, detonation charge, diamonds, modification, diffusion, structure formation, dispersion-hardened steels, wear.
Introduction To increase the service life of products in machine building, it is customary to restore their worn layers by surfacing. The efficiency of this technology is determined by numerous factors: formation of a high-quality transient layer, absence of defects, attainment of a homogeneous structure of the coating, getting of the required consumer properties, and minimization of the costs. The task of simultaneous realization of all these conditions represents a quite complicated problem. The researchers try to solve it by choosing electrodes (or wires) with optimal chemical compositions [1]. However, this approach cannot guarantee the formation of homogeneous structures and the absence of defects in the coating if the base metal is either a dispersion-hardened metal with heterogeneous phases or is contaminated by large amounts of nonmetallic inclusions, which float under the conditions of minor melting of the transition layer and are partially dissolved. This leads to the formation of liquation zones, stresses in the coating, and defects, as well as to the crumbling of the working surface in the process of operation. For the purposes of restoration of surfaces of worn articles in machine building, it is customary to use the procedure of modification of the liquid bath with insoluble carbon-containing diamond admixtures [2–5]. The proposed approach was first applied at the Kharkiv National Technical Agricultural University after the comparative analysis of the results of modification with special nano- and dispersed diamonds and also with a natural component (schungite). In this case, in the first stage of investigations, we used only dispersed 1 2
P. Vasylenko Kharkiv National Technical Agricultural University, Kharkiv, Ukraine. Corresponding author; e-mail: [email protected].
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