Fatigue Variability of Alloy 625 Thin-Tube Brazed Specimens

As an advanced heat exchanger for aero-turbine applications, a tubular-type was developed. To ensure the optimum performance of exchanger, it is necessary to assess structural integrity tubes, considering assembly processes such as brazing. In this study, fatigue tests at room temperature and 1000 K were performed 0.135 mm-thick alloy 625 tubes (outer diameter 1.5 mm), which brazed grip specimen. The variability in life investigated by analyzing locations failure, fracture surfaces, microstructures joint tube. At temperature, specimens failed near high ?max values, while both failure tube side observed low values. largest under same test conditions found when one specimen joint, other middle with showed multiple crack initiations circumferentially surface filler metal layer growth cracks tube, resulting short life. K, all exhibited case, short-life initiation along grains large through thickness addition carbides inside results suggest that thin-tube affected presence well spatial distribution grain size carbides.