Corrosion behavior of low-temperature plasma carburized AISI 420 steel - part I - effect of treatment temperature
Cristiano Scheuer1; Felipe Possoli2; Rodrigo Perito Cardoso3; Paulo César Borges2; Silvio Francisco Brunatto3
1 Universidade Federal de Santa Maria; 2 Universidade Tecnológica Federal do Paraná; 3 Universidade Federal do Paraná
doi:10.20906/CPS/CON-2016-0170
Resumo
The effect of plasma treatment parameters on the corrosion behavior of low-temperature carburized AISI 420 stainless steel was investigated by means of electrochemical measurements. The first part of this study (out of two), was conducted in order to evaluate the effect of the treatment temperature on the carburized samples corrosion resistance. Plasma carburizing treatments were performed at temperatures of 350, 400, 450 and 500° C, for 8 and 12 h. The corrosion behavior was evaluated through open circuit potential and cyclic polarization test, using a solution of 3.0% NaCl as electrolyte. To support the discussions on corrosion behavior, XRD, microstructural analysis, and hardness measurements were also carried out. The results showed that low-temperature plasma carburizing treatment produced a carburized layer consisting of two parts, an outer layer ('C + Fe3C) and a diffusion layer ('C). The electrochemical tests demonstrate that samples treated at temperatures between 350 and 450 °C exhibit higher corrosion potentials compared to untreated material, in the two studied treatment times. Moreover, the samples carburized at 500 °C showed lower corrosion potential compared to the untreated sample. Finally, an analysis of the corroded surface showed the predominance of pitting corrosion mechanism on samples treated at low temperatures (350-450 °C), intergranular corrosion for the samples treated at high temperature (500 °C), and widespread corrosion to the untreated sample.
Palavras-chave: low-temperature plasma carburizing; treatment parameters; martensitic stainless steel; expanded martensite; corrosion resistance; electrochemical tests