ABSTRACT Duplex stainless steel UNS S31803 exhibits high mechanical strength with high corrosion properties, due to its microstructure composed of ferrite and austenite phases, in equal proportion. When the UNS S31803 steel is submitted to high temperatures, some precipitations can occur, such as nitrites, carbides, and third phases (e.g. sigma phase -σ, and alpha prime - α'). These phases are deleterious in relation to the mechanical properties and corrosion resistance, and their effects are analyzed regarding the properties of the steel. In order to evaluate the precipitation of this deleterious phase, isothermal treatment was done at 500°C for 144 hours (α' phase) and at 850ºC for 80 minutes (σ phase). The results were obtained through the microstructural analysis and tensile tests. The presence of sigma phase was verified in the grain boundary, an increase in the mechanical resistance with a loss of toughness. There was as well as an increase in mechanical resistance with the precipitation of α', with less loss of ductility than that observed in the experiments involving the presence of sigma phase.

RESUMO O aço AISI 316L é muito aplicado como biomaterial de baixo custo em próteses e equipamentos cirúrgicos, dentre outras aplicações. Estas aplicações se devem à sua boa resistência à corrosão em presença de meios contendo fluidos corporais. Muito embora o aço apresente as características mencionadas, estas poderão ser comprometidas com a formação de martensita alfa linha (fase magnética) induzida por deformação a frio. Neste caso, o presente trabalho, teve como objetivo investigar os efeitos de laminação a frio no surgimento de fase martensítica. Para tanto foram realizadas três diferentes deformações. A chapa como recebida e as amostras deformadas foram submetidas a ensaios de ferritoscopia, microdureza Vickers e análise microestrutural por microscopia eletrônica de varredura, MEV. Foi observado que nas amostras deformadas a frio houve o surgimento de fase magnética (provavelmente martensita alfa linha) e aumento da microdureza, devido ao encruamento e à presença de fases induzidas por deformação.

ABSTRACT AISI 316L steel is widely used as a low cost biomaterial in prostheses and surgical equipment, among other applications. These applications are due to their good corrosion resistance in the presence of environment containing body fluids. Although this steel has the mentioned characteristics, it may be compromised with the formation of alpha prime martensite (magnetic phase) induced by plastic deformation. In this case, the present work aimed to investigate the cold rolling effects on the martensitic phase formation. For that, three different deformations were performed. The plate as received and the deformed samples were subjected to ferritoscopy, Vickers microhardness and microstructural analysis by scanning electron microscopy, SEM. It was observed that in cold deformed samples there was the magnetic phase appearance (probably alpha prime martensite) and microhardness increase, due to the hardening and the deformation induced phases presence.

ABSTRACT This work examined the pitting corrosion resistance of two types of duplex stainless steels: UNS S31803, with molybdenum, and UNS S32304, without molybdenum. Cyclic potentiodynamic polarization and critical pitting temperature (CPT) tests were performed in 3.5 wt% NaCl solution. Scanning electron microscopy (SEM) was used for analysis of the pits on the surface of samples. The two steels studied presented susceptible to pitting corrosion in 3.5 wt% NaCl solution. UNS S31803 steel showed a higher corrosion potential (Ecorr), pitting potential (Epit), and polarization resistance (Rp) compared to UNS S32304 steel. It was also observed that the UNS S31803 steel showed higher capacity to repassivation and CPT than the UNS S32304 steel.

Abstract This work aims to evaluate the performance of anticorrosive thermoplastic coatings in cold rolled steel sheets. Two types of thermoplastic coatings were studied: polystyrene (PS) and cornstarch. These types of coatings are applied for protection against corrosion during transport and storage of steel plates after cold rolling until delivery to stamping or other processing. The good performance for these coatings is suitably standardized to ABNT NBR 5915-2: 2013 and ASTM A1008 / A1008M-2016. According to corrosion tests carried out in saline chamber, the coatings were satisfactory in different degrees of guarantee of corrosion protection on ASTM 1080 steel, in accordance with standards mentioned.