| SM ISO690:2012|
PARAMONOV, Anatolii; PARSHUTIN, Vladimir; KOVALI, Alexandr; CHERNYSHEVA, Natalia. Receiving multilayer coatings by method of electrospark alloying. In: Materials Science and Condensed Matter Physics. Editia a 8-a, 12-16 septembrie 2016, Chişinău. Chişinău: Institutul de Fizică Aplicată, 2016, p. 315. ISBN 978-9975-9787-1-2.
|Materials Science and Condensed Matter Physics
Editia a 8-a, 2016
Conferința "International Conference on Materials Science and Condensed Matter Physics" |
8-th Edition, Chişinău, Moldova, 12-16 septembrie 2016
The electric spark alloying of surface is widely applied in mechanical engineering to increase of corrosion resistance of parts of machines, the tool and industrial equipment. It has number of advantages: strong cohesion of coating material with basis due to formation of solid solutions, and also chemical compounds; possibility of putting any conducting metals and alloys; lack of need for surface pre-treatment. The coated coverings also significantly improve physical and chemical properties of worked surface (hardness, wear resistance, etc.). However such shortcomings as high roughness, porosity and small continuity are inherent in alloying. Especially because of the last two, electric spark coverings cannot be used as cover, protecting substrate from corrosion. During researches the method of increase of corrosion resistance and wear resistance of steels due to forming of multi-layer coating with small roughness and porosity has been developed. It consists in the following: on substrate in turn it was applied several alternating alloy layers like BK8 (tungsten carbide) or TK (carbide of titanium) and cobalt on the modes with energy in impulse of 0,02-0,3 J with frequency of 200-1500 Hz, at the same time superficial plastic deformation of each layer was carried out. The last allows to receive each layer the most homogeneous and dense. Tests of method carried out as follows. Samples have been made of steel 45. On the ПЭЛ-28 installation they were alloyed first of all by BK8 alloy, then cobalt on the mode with energy in impulse of 0,08 J with frequency of 200 Hz. About 3 layers of BK8 and cobalt in turn have been put. Each put layer was subjected to the superficial plastic deformation (SPD) by hard-alloy roller. The surface roughness at the same time made Ra=0,8-1,9 micron, that allowed to carry out tests for friction. Corrosion tests carried out in electrolyte, g/l: NaCl 7.0 + Na2SO4 (waterless) 7.0 at current 10 mA within 1, 3 and 5 hours. Tests for wear hardness in the conditions of friction without lubricant carried out by the friction machine at loading 140H, the sliding speed of 0,3 m/s. As counterbody served samples from hardened steel 40X (HRC 55-58). As a result even coating coverings only from cobalt or only from BK8 leads to reduction of corrosion losses (even without SPD). Applying SPD to such coverings, reduce their roughness and increase density, narrowing amount of pores through which electrolyte gets to substrate, causing underetching of covering or even its partial fall. Coating on 3 layers in turn of BK8 and cobalt, with the subsequent SPD after each of them, leads to falloff of roughness of coverings. At the same time friction conditions even without lubricant use have significantly improved. Alloy of BK8 in itself and coverings from it is very much wearproof. But in practice it is very important that there was resistant all interface - detail and counterbody. Thanks to SPD there is reduction of surface asperity, sharp edges and tooth on surface of covering from BK8 and firmness of counterbody increases. It is very important that originally BK8 alloy and then cobalt was applied on detail. Thanks to that considerably improves wear-in coupling, decreases or even cockiness is liquidated, wear of counterbody significantly decreases, and interface serves much longer.