Regularities of Formation of Structural–Phase States on a Surface of Metals and Alloys at an Electroexplosive Alloying

• Main Author: D. A. Romanov, V. E. Gromov, Е. А. Budovskikh, Yu. F. Ivanov
• Format: Article
• Language: English
• Published: G. V. Kurdyumov Institute for Metal Physics of the N.A.S. of Ukraine 2015-06-01
• Series: Успехи физики металлов
• Online Access: https://doi.org/10.15407/ufm.16.02.119

For the first time, the quantitative and qualitative studies of the structural–phase states of the surface layers of metals and alloys subjected to electroexplosive alloying with the use of thermoreacting components are carried out. Using layer-by-layer electron-microscopy studies, a gradient character of the structural–phase states is revealed; it is characterized by a natural change of the phase composition and parameters of the defect substructure as the distance from the treatment surface rises. The main factors and mechanisms, which determine the acceleration of physicochemical synthesis processes of new phases at electroexplosive alloying, are revealed and analysed. As established, the electroexplosive alloying is caused by complex thermal-force effect on the irradiated surface of multiphase plasma jet formed from the products of electric explosion of conductors and powder samples and is accompanied by complex patterns of change in the structural–phase states and defect substructure at different (from macro- to nano-) scale levels. It is accompanied during a short treatment time equal to 100 μs as follows: for the case of aluminium alloying with nickel, with the formation of alloying zone strengthened with intermetallics of Ni–Al systems and characterized by great depth; for the case of titanium alloying of the surface of a solid WK10KS alloy, with the decomposition in the alloying zone of WC carbide particles and the formation of TiC, (Ti, W)C and W2C carbide particles; for the case of carboborating of the titanium surface, with the use of powder sample of amorphous-boron forming the layer of composite coating with the thickness of about 10 microns, which has the high microhardness (up to 3600 HV). Multiple increases of the microhardness, wear resistance, and other functional properties of the surface due to the electroexplosive alloying are ascertained. The regularities and formation mechanisms in the structural–phase states of the surface layers at an electroexplosive alloying with the use of thermoreacting components are revealed. The obtained research results can be used for the development of the theory of structural–phase transformations in metals and alloys and used in cost-beneficial technological processes for hardening the device surfaces in metallurgical, machine-building, aviation, and other industries. The acceleration of the synthesis of chemical compounds on the surface of metals and alloys at electroexplosive alloying is established experimentally. It consists in the formation of new phases and compounds with a rate exceeding the rate of their formation under the normal interaction conditions, if the pulsed plasma jets exposing the surface are formed from the products of electrical explosion of conductors, the exposure time is equal to 100 μs, the power density is of the order of several GW/m2, and the pressure in the shock-compressed layer near the irradiated surface is of about 1–10 MPa.