Characteristics of cementite formation in the surface layer of flake graphite cast iron formed by plasma transferred are remelting

Using the plasma transferred are (PTA) process to conduct surface remelting , the surface region of flake graphite cast iron can be hardened. To study the effect of silicon content on the microstructure of the hardened surface layer, flake graphite cast iron specimen of about 3.1 similar to 3.2 wt pe t carbon and various silicon contents from 1.47 to 3.41 wt pet were selecte d for the PTA surface remelting experiment. The remelting current and volta ge were set at 100 A and 32 V. The results show a rapidly solidified micros tructure with large amounts of eutectic cementite. Reducing the silicon con tent increases the volume fraction of eutectic cementite and thus increases the hardness, The increase of cementite volume fraction with decreasing si licon content is linear. Reducing the silicon content is also effective in suppressing the formation of porosities.