An experimental study was conducted not only to optimize the friction welding(FRW) conditions for the dissimilar heat resisting materials(IN713C-SCM440) of turbine impeller, but also to investigate the quantitative relationship between the weld quality of strength and toughness and the total number of acoustic emission(AE) counts. A quantitative correlation between the total number of AE counts and the weld quality appears to exist, and the optimum weld quality more than 100% of joint efficiency can be detected in real time during processing by the use of AE techniques. It seems likely that extension of this study could lead to the development of an in-process quality monitoring system the friction welding based on the acoustic emission events.
Friction welding is a solid state welding process. It makes use of the frictional heat generated at the rubbing surfaces to raise the temperature at the interface high enough to cause the two surfaces to be forged together under high pressure. Friction welding has been shown to have significant economic and technical advantages. However, one of the major concerns in using friction welding is the reliability of the weld quality. No reliable nondestructive test method is available at present for detecting weld quality, particularly in a production environment. Efforts have been made to detect weld strength nondestructively using ultrasonic methods. Unfortunately, the results were difficult to interpret; also, applications were limited to a certain weld geometry where side reflections of the ultrasonic wave were not significant. This paper presents a new approach which attempts to develop an in-process quality monitoring method for friction welds by using acoustic emission(AE) techniques. In this investigation, the acoustic emission counts were measured during plastic deformation of the welding process to correlate the weld strength for friction welds over a wide range of process conditions.
