Microabrasion-corrosion resistance of Ni-Cr superalloys deposited by plasma transferred arc (PTA) welding

Microabrasion-corrosion tests were carried out to investigate how small changes in dilution affect abrasion-corrosion resistance of Ni-Cr PTA welded deposits onto carbon steel. For each specimen, corrosion tests, microabrasion tests and combined microabrasion-corrosion tests were conducted. Potentiodynamic corrosion tests under aerated conditions used three different electrolytes. Abrasion resistance was evaluated using a fixed-ball microabrasion test rig, for slurries of SiO2 in distilled water (20 wt%). Microabrasion-corrosion tests used SiO2 slurries for the same electrolytes used in the corrosion tests under potentiodynamic conditions. For the most aggressive electrolyte (NaCl + H2SO4 solution) it was possible to identify small variations in current density with dilution in the microabrasion-corrosion tests, whereas no significant differences were identified for the other electrochemical variables. However, as a general trend, all deposits presented high abrasion-corrosion resistance, evidencing that small variations in dilution do not compromise their performance for the conditions tested. As expected, the wear coefficients measured under microabrasion-corrosion conditions were higher than under pure microabrasion conditions. On the other hand, friction coefficients for microabrasion-corrosion were lower when compared with conventional microabrasion tests for all the slurries tested. This was apparently due to how the passive film affects particle entrainment during the tests.