Magnetron-sputtered oxidation protection coatings for Mo–Si–B alloys

• Oxidation protective layers were deposited on Mo–Si–B alloys by magnetron sputtering.
• The oxidation behavior was studied at 800, 1000, and 1300 °C in air.
• An aluminum borate scale formed on the Mo–70Al layer.
• Mo–37Si–24B and Mo–46Si–24B coatings were protective at 800 and 1000 °C for up to 100 h.
• The Mo–46Si–24B coating was protective for short times even at 1300 °C.

Oxidation protective Mo–70Al, Mo–37Si–15B and Mo–46Si–24B (at.%) coatings with 5–10 μm thickness were deposited on Mo–9Si–8B alloys by magnetron sputtering; and their oxidation behavior was studied at 800, 1000 and 1300 °C in air. On the Mo–70Al layer a dense aluminum borate scale grew at 800 °C; however, this coating rapidly degraded at 1000 °C linked to substrate oxidation at uncoated areas. The Mo–37Si–15B and Mo–46Si–24B layers provided oxidation protection to the Mo–Si–B alloy at 800 and 1000 °C for up to 100 h due to formation of a borosilicate scale. The latter coating was protective for short times even at 1300 °C.