Measurement of microhardness of multilayer metal material obtained by electroslag remelting

Application of electroslag technology for metallic materials is highly variable and allows to influence the structure of the resulting casting in a variety of ways. One of such methods is obtaining a multilayer preform. According to our proposed technology formation of layers of new composition was carried out by supplying of carbonaceous material of given weight to the liquid metal bath at specified intervals. In order to determine the changes caused by the introduction of additives, a series of mechanical tests were carried out, and in particular, the microhardness of the resulting material was determined. Microhardness measurement in metallographic studies yields results that are not possible to achieve with macroscopic mechanical tests. For example, the pattern of change of hardness values in a multi-layer metal composition can be identified. Determination of microhardness of multilayer metal composition was performed with a “Thixomet” platform (St. Petersburg). Hardness was measured with Buehler Micromet 6040 microhardness tester equipped with motorization and Thixomet software, using a four-sided diamond pyramid under a load of 200 gf. The study was conducted in accordance with ISO 6507-1 : 2007. Analysis of the data allows to conclude that microhardness of the material with a great amount of additives is higher than of those with a smaller amount of carburizers; microhardness is higher on transverse specimens than longitudinal ones; samples subjected to a deeper degree of deformation and to heat treatment (annealing or annealing + tempering) have microhardness almost two times higher. It is also worth mentioning that great degree of deformation leads to a smearing of the material layers in the structure, and defines the maximum degree of deformation of the material that preserves the multilayer structure.