Debonding Filure Of T-type Stainless Steel Brazing Joint Under High Temperature

The stainless steel plate-fin heat exchanger is widely used in the field of nuclear power because of its compact structure,high heat transfer efficiency and low manufacturing cost.The plate-fin structure of the heat exchanger is made by brazing technology.Due to the structural discontinuities and mismatched mechanical properties,cracks will easily initiate and propagate in brazing joints when the equipment serves in long time under high temperature,high pressure or other harsh environments.Once the crack reaches the critical size,the heat transfer equipment fails.However,the failure mechanism of the brazed joint is not clear and lack of complete and reliable mechanical performance test.Therefore,it is very important to study the high temperature mechanical properties and failure mechanism of the brazed joints of the plate-fin structure.It is found that the failure form of the plate-fin structure of compact heat exchangers is similar to the adhesive stripping.In the present study,the peeling performance of the brazed joint with different structural parameters and test parameters is studied by means of the peeling tests.Then the debonding failure mechanism of brazed joints is investigated by microstructure analysis.The main research contents are as follows:1)The load displacement curve is obtained through peeling tests of the T-type brazing joint subjected to high temperature.Based on this,characteristic parameters of peeling properties,such as the maximum peel strength,average peel strength and fracture energy,were obtained.2)The effect of the thickness of the base metal,the loading rate,the filler metal thickness and the test temperature on the peeling properties of T-type brazing joints were analyzed.The reasonable structural dimensions and test conditions of T-type brazed joints were summarized and given.3)The element distribution in bonding region was investigated by means of SEM and EDS energy spectrum technology.The characteristic regions were divided according to the element concentrations.Finally,the failure mechanism of brazing joint with different structural parameters and service conditions was analyzed.