The bubbling potential of molybdenum and its alloys in soda-lime-silica glass

Molybdenum alloys have many uses in glass manufacture because of their high creep strength and chemical inertness. However, the presence of high concentrations of carbon, a requirement for increasing molybdenum's strength, can result in bubble generation at the metal-glass interface. Experimental determinations of the bubble potential of molybdenum and its alloys are presented. The differences in bubbling potential of molybdenum and its alloys are related to their free carbon content and the stability of the microstructure. The more stable the microstructure is and the lower the free carbon content is, the lower the bubble potential. Higher carbon levels in molybdenum in the form of carbides having high free-energy of formation can be tolerated in grain-stabilized molybdenum alloys subjected to soda-lime-silica glass contact. Both of the grain-strengthened molybdenum alloys exhibited a commercially-acceptable bubble potential up to a temperature of 1370 degree C. However, the HfC-Mo alloy should perform better at 1370 degree C than would the TiC-ZrC-Mo alloy. It was verified that arc-cast molybdenum will produce a high level of bubbles in soda-lime glass