Experimental study on peeling performance of T-type brazing joints

Abstract As a promising heat transfer component of high temperature gas cooled reactor (HTGR), the performance of the plate-fin heat exchanger determines the energy efficiency and life of the HTGR. Although the plate-fin structure has lots of advantages such as high efficiency, compact structure, low manufacturing cost, its performance is greatly affected by the vacuum brazing technology and harsh conditions, e.g. high temperature and high pressure. In the practical application, “peeling” failures may occur in the brazing joint between the fin and the parting sheet. It becomes necessary to characterize the strength of the joints. However, the standard specimen cannot accurately describe the real stress distribution. In the present study, a T-type specimen is designed for the peel test of brazing joints. To reflect the influence of brazing seams and thickness of the base metal, five specimens are designed and tested under 25 °C, 450 °C, 550 °C and 650 °C with five different applied loads, respectively. Based on the bilinear hardening model, the peeling performance of all T-type joints are obtained according to the tested peeling force-displacement curves. Then the influences of base metal thickness, brazing seam, loading rate and test temperature on the peeling performance are analyzed. The results show that the maximum peel force, the average peeling force and the fracture energy all decrease as the results of increased base metal thickness. With the increase of the filler thickness, the average peeling force and the fracture energy of the brazing joints both decrease. 0.95 mm thick base metal and two layers of brazing filler metal are recommended for brazing joints. The loading rate of the peel test has no significant effect on the average peeling force and the fracture energy.