Study of corrosion and microwear resistance of AISI 321 austenitic stainless steel

The austenitic stainless steel AISI 321 is stabilized with titanium, and thus, it has high resistance to sensitization and is used to manufacture equipment for the petrochemical, chemical, and fertilizer industries. In this work, the behavior of solution-treated AISI 321 stainless steel in resistance to abrasive microwear by fixed ball and corrosion by cyclic polarization was studied. Samples with 25.4mm in diameter and 12.5mm thickness were used. The samples were ground and polished according to ASTM E3-2015 standards. The abrasive microwear tests by fixed ball were performed in triplicate with a load of 8N, 150RPM, and test times of 300, 600, 900, 1200, 1500, and 1800 seconds. Electrochemical tests were performed to obtain the corrosion potential, pitting potential, current density for passivation, and passive current density. A classical electrochemical cell with three electrodes with a working area of 1 cm2, a reference electrode of Ag/AgCl (KCl sat), and a counter electrode of platinum was used. The electrolyte used was a 3.5% NaCl solution. The worn volume increased with the distance traveled and in the permanent wear regime, the wear rate was 5.4125x10-5 ± 0.037x105 (mm3/Nm). The AISI 321 stainless steel presented a corrosion potential of Ecorr of 0.041 V, a pitting potential of Epite of 0.535 V and after the pit's opening, passivation occurred. The presence of nitrogen and low titanium content in the chemical composition of the austenitic stainless steel AISI 321 led to the formation of TiN. The interface between titanium nitride and the austenitic matrix facilitated the micro galvanic reaction, producing current density fluctuations in the anodic polarization curve.