Efeitos da adição de B, Y2O3 e/ou WS2 na microestrutura e no comportamento tribológico do aço inoxidável austenítico produzido por SPS

Abstract

Austenitic stainless steels are alternatives to meet the demand for advanced materials for applications that aim to reduce energy consumption and deterioration of components due to tribological phenomena such as friction and wear. For this, these steels may have added additives and reinforcements to their composition through the use of sintering processes. These additives and reinforcements have different roles: sintering agents, such as boron (B), aim to increase densification; mechanical reinforcements, such as yttrium oxide (Y2O3), aim to improve mechanical properties; and solid lubricants, such as tungsten disulfide (WS2), aim to increase the lubricity of the material. Thus, the materials may have properties that allow them to be used in tribological applications. Therefore, the objective of this work is to evaluate the effect of the addition of B, Y2O3, and WS2 on the tribological properties of 316L austenitic stainless steels produced by spark plasma sintering. To better understand the tribological behavior of the material, a detailed study aimed to identify the crystalline phases of the materials, using techniques such as SEM, EDS, and DRX and by thermodynamic study, to understand the microstructure of the material and correlate it with the effects of friction and wear. Other analyzes such as density and hardness also corroborated with the study. Microstructural analysis revealed that the addition of B and WS2 favored the closure of pores and increased the hardness of the material. In turn, the addition of Y2O3 provided an increase in porosity and a decrease in hardness. In addition, it was possible to verify the formation of new phases during sintering, in which the elements of the austenitic matrix reacted with the elements of the additives and reinforcements. These microstructures were not able to decrease the levels of the materials, which maintained a friction coefficient higher than 0.6. In turn, the level of wear varied according to the microstructure and other material properties. B and WS2 tend to decrease and Y2O3 tends to increase the specific wear rate. The friction levels were governed mainly by adhesion mechanisms and the wear levels, by adhesion, abrasion, and oxidative mechanisms. [resumo fornecido pelo autor]