Structure and properties of hot-deformed powder steels microalloyed by aluminium

Abstract

The feasibility of cohesion degree enhancement, mechanical properties, and contact durability of powder forged steels due to microalloying with aluminum was studied. Unalloyed iron powders with various impurity contents, as well as atomized powder of low-alloy chromium-molybdenum steel, were used as the basis for the producing mixtures. Aluminum was doped as ferroaluminum. Specimens for mechanical and fatigue tests were produced by powder forging. Post-heat treatment was carried out according to two flow routes. The first flow route included carburizing, hardening and low tempering. The second flow route corresponded to high-temperature thermomechanical processing, which was carried out immediately after the completion of hot repressing porous preform. It was found that doping aluminum microadditives in hot-deformed powder steels provides the feasibility of increasing bending strength, impact strength and fatigue life under contact or low-cycle loading. This is associated with an enhancement of the conditions for interparticle joining during hot forging due to the generation of interlayers of ferrite in the interparticle zones as well as to the activation of cohesive interactions as a result of accelerating the process of dynamic recrystallization