Abstract
Wettability and interaction between ferritic spheroidal graphite cast iron and silver-base brazing alloy melts were studied to attain the higher interfacial strength and reliability of bonding. Wettability was estimated by sessile drop method. At 1023 K, the contact angles of molten Ag-Cu eutectic alloy melt were about 60° to the spheroidal graphite cast iron containing 13 vol.% graphite nodules, 150° to graphite substrate and 20° to Fe-Si-Mn alloy with the almost same composition as that of cast iron matrix, which satisfied the Cassie's equation for the wettability to composite materials. Although zinc lowered liquidus of brazing alloy below the eutectoid temperature of cast iron, it impaired the wettability. The addition of manganese to the alloy decreased the contact angle to about 60°. The thin Mn rich layer containing about 60% manganese appeared at the interface between brazing alloy and cast iron, which was identified as α-Mn by analytical electron microscope. The enrichment of manganese at the interface should improve the wettability.
