The influence of Si concentrations on the oxidation resistance of Mo-Si-B-(N) coatings

The influence of the silicon concentration on the oxidation resistance of Mo-Si-B-N coatings prepared by magnetron sputtering is investigated. The Si content in them was controlled by the composite-target composition, as well as by various areas of silicon segments placed into the target-erosion zone. The composition and structure of coatings after deposition and annealing in air at temperatures of 500-1300A degrees C are investigated using transmission and scanning electron microscopy, energy-dispersive analysis, and glow-discharge optical emission spectroscopy. It is established that oxidation resistance increases as the Si concentration in coatings increases, which is caused by the formation of a silicon oxide-based dense layer; this layer prevents oxygen propagation into the coating depth upon heating. The maximal oxidation resistance at a level of 1300A degrees C is attained in Mo-Si-B-N coatings containing 40 at % Si.