Estudo do revenimento no aço SAE 1045 durante o tratamento de nitretação à plasma

Abstract

AISI/SAE 1045 steel is widely used in the industry due to its combination of good mechanical properties and low cost. As a medium carbon steel, its properties can be adjusted through the application of heat treatments. Quenching, for example, is used when seeking to significantly increase the material's hardness. However, this process compromises toughness, which is why it is commonly followed by tempering, which aims to partially recover this property. In situations where even higher surface hardness and greater wear resistance are desired, plasma nitriding can be used—a thermochemical treatment carried out in an ionized, nitrogen-rich atmosphere. Considering that tempering is frequently performed at temperatures compatible with the plasma nitriding process (400°C), this study aimed to investigate the effects of simultaneously performing the tempering of quenched 1045 steel with the plasma nitriding treatment, targeting the optimization of the processing cycle. The methodology involved preparing SAE 1045 steel samples that were subjected to four experimental conditions: quenched (Q), quenched and tempered (QT), quenched and nitrided (QN), and quenched, tempered, and nitrided (QTN). All tempering and nitriding treatments were performed at a temperature of 400°C. The samples were characterized by Vickers microhardness tests (surface and profile), optical microscopy, and surface roughness tests. The surface microhardness results confirmed the success of nitriding, with the QN sample exhibiting the highest surface hardness values. The analysis of the microhardness profile and the microstructures demonstrated that the QN treatment was effective in promoting both surface hardening through nitride formation and adequate core tempering in a single step, resulting in an optimized property profile. Simultaneous tempering and nitriding (QN) proved to be a viable alternative to reduce the cycle time, providing the material with high surface hardness, combined with a tough core, and avoiding the costs of a separate tempering step.