Laser beam cladding characteristics of hastelloy on cast iron

摘要

CO{sub}2 laser beam was applied to the cladding of hastelloy C on cast iron using a preplaced powder method. The hardness and microstructure of the clad layer were investigated by changing the laser power and number of clad layers. The average hardness of the clad layer obtained was 300-350 HV0.1, when the conditions were as follows : laser power of 2300 W to 2700 W, clad number of one layer to two layers (thickness of clad layer; 0.85-1.90 mm), cladding speed of 400 mm/mm, defocusing distance of 30 mm, oscillation width of 7 mm and argon as the shielding gas. The microstructure of clad layer was completely transformed into the fine dendritic structure (secondary dendrite arm spacing; 3μm) and eutectic structure by the rapid solidification. A heat affected zone was produced on the surface of the cast iron. The heat affected zone was heat treated with electric furnace at 873 K; the martensitic structure of the heat affected zone was transformed into pearlite. The hardness of the clad layer was unchanged with heat treatment. EPMA line analysis indicated that an alloyed layer (thickness; 60μm) exists between the clad layer and base metal. These results show that CO{sub}2 laser beam cladding of hastelloy C serves as a new surface treatment process for cast iron.