Síntese e caracterização estrutural de compósitos de aço duplex uns S31803 com carbeto de cromo, carbeto de vanádio e metanol

Abstract

Duplex stainless steels (AID), which have a biphasic microstructure with approximately equal proportions of ferrite and austenite, are widely used in high performance components for the gas, nuclear, chemical, and paper industries, due to their superior combination of corrosion resistance and mechanics. When produced using the powder metallurgy process, it is possible to improve some properties, such as hardness and wear resistance. In this work, samples of AID UNS S31803 steel with the addition of Cr3C2 or VC and without additions were produced via powder metallurgy, using high energy grinding. For this purpose, AID UNS S31803 steel chips were milled without additions, with the addition of 3% by weight of Cr3C2 or VC and with the addition of 3% by weight of Cr3C2 or VC adding 1% by weight of methanol as Process Control Agent (PCA), for the times of 20h, 40h and 60h. The powders milled for 40h and 60h were sintered at 1250°C for 1 hour, under an argon atmosphere. The powders were characterized for particle size and morphology using sieving, laser granulometry and Scanning Electron Microscopy techniques (SEM). The phases that make up steel were evaluated before and after the X-ray diffraction (XRD) grinding processes. After sintering the samples were evaluated for porosity and densification, using the optical microscopy technique and the Archimedes method, respectively. The results showed that the addition of carbides and process controlling agent in high energy grinding increased the grinding efficiency, as it was observed that a larger volume fraction of smaller particles was obtained. Among the conditions studied, steel milled with additions of vanadium carbide and methanol was the most efficient. After the sintering step, the samples with the lowest porosity were those ground with the addition of vanadium carbide and methanol, with a surface porosity of 2.19% and a density of 5.13 g/cm3.