Tribocorrosion study of martensitic and austenitic stainless steels in 0.01 M NaCl solution

In this study, types 440B (martensitic) and 304 (austenitic) stainless steel were subjected to microstructural characterisation and a series of tribocorrosion tests in a pin-on-disc facility equipped with a corrosion cell, in order to obtain understanding on their tribocorrosion behaviour in 0.01 M NaCl solution under the loads up to 5 N. The results from tribocorrosion tests revealed that, as compared to pure corrosion, open circuit potential of the materials under the applied load shifted towards negative direction and the measured current density correspondingly increased. Potentiostatic tests enabled tribocorrosion behaviour of the materials to be investigated at constant potential values that represent different oxidising capacities of the solution. It was shown that volume losses by wear were independent of potential and test material. In contrast to this, volume losses by corrosion increased with increase in potential for type 440B stainless steel, while those by synergetic effects of corrosion and wear grew with increase in potential for both test materials and become the key damage mechanism under oxidising conditions. However, corrosion attack was local, causing actually more dramatic effects on material losses (through synergy) than disclosed solely by volume losses by corrosion, and clearly linked with the material microstructure. In this paper, these results are presented and discussed in the light of alloy repassivation capability.