LAUSR

During operation of gas turbine engines, different salts develop that lead to a hot-corrosion attack. While the hot corrosion associated with Na 2 SO 4 and Na 3 VO 4 has received considerable attention, MgSO 4 is also a main salt component, but it has received limited examination. For operation at temperatures beyond the capabilities of Ni-base superalloys, refractory-metal alloys with a Mo–Si–B-based coating have demonstrated a robust environmental resistance including hot corrosion attack by Na 2 SO 4 and Na 3 VO 4 . In order to evaluate the performance of Mo with a Mo–Si–B-based amorphous coating, samples were exposed to MgSO 4 under thermal cycling at temperatures from 800 to 1300 °C. Mass change measurements revealed minimal attack from the MgSO 4 exposure except in local regions where cristobalite and MgMoO 4 were detected. Even with the local region reaction, the mass change after a cumulative 100 h of exposure was about 3.5 mg/cm 2 . Exposure to a composite salt mixture containing Na 2 SO 4 , NaVO 3 , MgSO 4 , CaCl, and KCl revealed signs of interactivity compared to the corrosion due to the separate effects of the individual salts, but again the mass change stabilized to a minimal level demonstrating that the Mo–Si–B-based coating is resilient to hot corrosion.