Effects of Tool Geometry on Hardened Layer of Friction Stir Processed Cast Iron

Abstract

The authors clarified that various cast irons can be hardened by friction stir processing (FSP) in a previous study. However, the high applied tool load was indispensable for obtaining the hardened layer. In this study, the effect of the tool geometry on the applied tool load was investigated for forming the hardened layer by the FSP with a lower applied tool load. As a result, the applied tool load could be reduced by 36% using a concave tool.

Surface Hardening of Ferritic Flake Graphite Cast Iron by Friction Stir Processing

“…This phenomenon is quite different from that of spheroidal graphite cast iron. 20) In the case of spheroidal graphite cast iron all of the graphite nodules are located independently among the matrix, and the matrix is observed to keep a very good continuity condition. However, in a case of a flake graphite cast iron many long and thin graphite flakes are observed to divide the matrix into many small and fine units of matrix.…”

“…20) The surface hardening of the ferritic flake graphite cast iron also required the diffusion of the carbon into the matrix and the high cooling rate, as shown in Fig. 6.…”

“…18,19) It was clarified that Vickers hardness of about 700 HV can be obtained due to the formation of the fine martensite even in the low hardenability ferrite-based spheroidal graphite cast iron without any pretreatment. 20) In this study, the FSP conditions are optimized for the surface hardening of the ferritic flake graphite cast iron (FC100), and the changes in the microstructure and the hardness by the FSP are investigated.…”