Effect of Process Variables on Microstructure and Mechanical Properties of Wide-gap Brazed IN738 Superalloy

摘要

This study investigated the microstructure and mechanical properties of a wide-gap region brazed with various process variables. The IN738 and DF 4B alloy powders were used as additive and filler metal powder for the brazing process. The wide-gap brazing process was carried out in a vacuum of 2 × 10{sup}(-5) torr. The wide-gap region brazed with 60wt.% IN738 additive powder had a microstructure consisting of IN738 additive and (Cr, W){sub}2B. The fracture strength of the wide-gap region (60 wt.% additive and 40 wt.% filler metal powder) brazed at 1230°C for 30hr was as high as 862MPa (93% of base material strength). It was observed that the brazing temperature was the main process variable affecting the mechanical properties of the wide-gap brazed region. The creep rupture life of the region brazed with 60wt.% additive and 40 wt.% was longer than that of other brazed samples. The Cracks in the wide-gap brazed region initiated at the (Cr, W){sub}2B and propagated through them. It was found that the (Cr, W){sub}2B and the pore in the brazed region are important microstructural factors affecting the mechanical properties of the wide-gap brazed region.