Microstructure and wear properties of silicide based coatings over Mo–30W alloy

• Molybdenum silicide based oxidation resistant coating has been formed over the Mo–30W.
• Mechanism of formation of single and double layer coatings has been presented.
• Wear tests showed a marked improvement of wear resistance of coated alloy as compared to uncoated alloy.
• Double layer coated sample showed improved crack and wear resistance.

The paper deals with the microstructure and wear properties of the Mo-30W alloy, coated with silicide based oxidation resistant coatings using pack cementation technique. The microstructure of the coating revealed that the coating was free of cracks or pores, adherent to the substrate and comprised of either single layer or double layer depending the coating temperature. Scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) was used to determine diffusion profiles for Mo, W and Si. Reciprocating sliding wear and friction experiments were performed on the uncoated and coated alloy. Double layer coating showed an improved friction coefficient as compared to base alloy as well as a single layer coated alloy. The wear tests also showed a marked improvement of wear resistance of coated alloy as compared to uncoated alloy. The coating was found to be wear resistant at 7 N.