Effect of heat treatment on deformation inhomogeneity of carbon steel / stainless steel bimetal

Abstract

The work is devoted to the study of the effect of annealing on mechanical properties and inhomogeneity of plastic deformation of a bimetallic plate made of stainless / carbon steel with the dimensions of the working part 50×7×2 mm. To develop laser technology for producing bimetals of various compositions, the contact zone of two dissimilar steels is of greatest interest. Since the performance characteristics of the entire product as a whole depend on the structure and properties of this zone, interaction of the components of the bimetal in the process of its manufacture leads to appearance of heterogeneity of various types near the interface and in the volumes adjacent to it. The research material was obtained by laser cladding of wire AISI 304 stainless steel on a plate of low-carbon steel St3. Bimetallic samples were subjected to vacuum heating at a temperature of 700 °C at various times from 2 to 8 h. The use of data on the distributions of local strains by the speckle photography method made it possible to consider the process of plastic flow in the initial section of tension diagram and to establish the effect of annealing temperature on plastic strain localization during mechanical tests. For a quantitative assessment of deformation inhomogeneity in the main and cladding layers, we used spatiotemporal distributions of local elongations and the corresponding values of the variation coefficient. It was established that the level of deformation inhomogeneity of microvolumes at the interface during tension is higher than that of the bimetal main layers. With increase in the annealing time, increase in the variation coefficient in the joint zone is noted, which is more significant on the stainless steel side, and this increases the probability of microcracks initiation. The increased level of deformation inhomogeneity of microvolumes of the cladding layer carburized zone is contingent on the increased localization of deformation in nearby microvolumes due to structural heterogeneity.