| 摘要 |
PURPOSE:To increase the oxidation resistance of an exhaust pipe and secure the high-temperature fatigue strength while preventing the oxidation scale from peeling off by forming an Al diffusion layer containing rare earth elements on the inner-wall surface of an exhaust pipe made of an iron series material at a specific thickness. CONSTITUTION:In a cast iron exhaust pipe 8 connecting the combustion chamber of an engine 1 to a turbo supercharger 4 and a stainless steel exhaust pipe 7 extended to the rear of the car body from the turbo supercharger 4, an Al diffusion layer 10 containing rare earth elements is formed on the inner-wall surface of an iron series base material 9 at a thickness of 50-150mu. The Al diffusion layer 10 is constituted with a compound layer 11 located at the surface side and a diffusion layer 12 at the iron series base material 9 side. Accordingly, the adhesion, to the exhaust pipe, of the oxidation scale generated by rare earth elements on the inner wall of the exhaust pipe is increased, the Al diffusion layer can be made thin, and the high-temperature fatigue strength of the exhaust pipe can be secured while the oxidation scale is prevented from peeling off. |
