Abrasão-corrosão em aços inoxidáveis ferríticos

Abstract

The aim of this work was to study the behavior of ferritic stainless steels in abrasive-corrosive environment of 10%wt SiO2 + 1N H2SO4. It was developed an apparatus and a methodology to perform the tests. The equipment has a load cell to measure the normal and friction forces during the test, an original device due to the difficulty to use it without damaging in abrasivecorrosive environment. It was used samples of ferritic stainless 11Cr, 11CrTi, 16Cr, 16CrNb (Nb stabilized) and, for comparative purposes, the stainless steels 18Cr8Ni (austenitic), 17CrTiNb (ferritic) and the carbon steel A36. It was proceeded the mechanical characterization (hardness and tensile testing), chemical and metallographic test (grain size) of these samples. For 16Cr and 16CrNb steels the crystallographic texture was analyzed, by EBSD. It has been realized corrosion test at turbulent and aerated environment, abrasion and abrasion-corrosion test. So it was analyzed the polarization curves, the wear coefficient k and the samples, by SEM. It was clearly observed at the corrosion tests the increasing at corrosion resistance with the increasing of Cr content in the samples. Although the 18Cr8Ni was the hardest material, it had worse performance on the abrasion tests. In this abrasive system studied there was a wear resistance increased after prior cold deformation. For the abrasioncorrosion tests the 18Cr8Ni had the best performance, although it was the worse in abrasion test. The materials were ranked by the higher wear resistance due to the increasing Cr content that was associated to the corrosive influence on the total wear in this abrasive-corrosive environment. In abrasive-corrosive medium, the wear was lower when compared to the abrasive medium for all materials mainly due to the friction coefficient reduction. For the steels 16CrNb and 16Cr, it was observed a slight influence of crystallographic texture on the corrosion resistance in turbulent medium and abrasive wear. However, this distinction does not exist for the abrasion-corrosion tests. It was also noticed an influence of niobium carbides in reducing the wear coefficient, even in a soft matrix as 16CrNb steel.