Study of special properties of austenitic steel, obtained by additive hybrid technologies

Abstract

An experimental and theoretical study has been carried out to analyze the impact of interlayer forging in the process of hybrid additive manufacturing on the development of fracture under dynamic and multicycle loading, which is relevant for justifying the models for estimating the resource of austenitic steel products. It has been established that forging significantly affects the strength of synthesized steel during quasi-static and dynamic testing, as well as the fatigue resistance during classical multicycle fatigue failure. It was found that interlayer forging leads to a decrease in the signs of trans-crystallization of the deposited metal and an increase in the proportion of equiaxial dendrites in the AISI 308LSi structure, which contributes to an increase in these characteristics during dynamic and multicycle loading of steel obtained by hybrid additive deposition. In the quasi-static range of strain rates, the tensile strength of deposited steel (with forging) reaches 810–820 MPa, which is 10% higher compared to the analog obtained by deposition without forging. Under the strain rates ranging from 10² to 10⁴ s⁻¹, the tensile strength of deposited steel (with forging) reaches 1400 MPa, which already exceeds the strength of the material deposited without forging by 17% (or 200 MPa). Interlayer forging during deposition significantly increases the resistance of steel to multicycle fatigue: σ_max of the deposited material in the vertical and horizontal directions at a number of cycles above 200,000 exceeds σ_max of the sheet material, while at 10⁷ cycles, the material can withstand a maximum stress of 360–375 MPa, which exceeds the level of the sheet material by 10%.