Influence of the thermal cycle on microstructure formation during direct laser deposition of bainite-martensitic steel

Abstract

The article presents the formation of structure and mechanical properties of bainite-martensitic steel in the process of exposure to a laser source. By varying the inter-pass temperature, the thermal cycles take place in a different temperature range, at which the formation of martensite and metastable austenite occurs. The formation of residual metastable austenite has a significant impact on the mechanical properties and performance of the product. During continuous growth, the process of phase transitions takes place in the high-temperature region. In the high-temperature region and slow cooling, bainite ferrite forms. The ferritic structure leads to brittle fracture at negative temperatures, which is unacceptable in cold-resistant steels. When specimens are deposition with a pause, the formation of the structure occurs in the low-temperature region, forming mainly bainite-martensitic structures. The resulting properties are quite high, but anisotropy is also preserved.