Investigation on Microstructure and Compressive Strength of Brazing Porous Nickel to Copper and Stainless Steel

Abstract

This paper investigates the effects of brazing temperatures on the microstructure and compressive strength for brazing porous nickel to copper and stainless steel using VZ2250 as the brazing filler metal. A high vacuum furnace is used to braze the samples. Three different brazing process parameters were set with a heating and cooling rate of 10°C/min, respectively. The characteristics of the joint interface have been investigated to evaluate the performance of the brazed samples by use of scanning electron microscope, energy-dispersive X-Ray spectroscope, X-Ray diffractometer, and Instron Universal Testing machine. The data obtained has been quantitively analyzed to confirm the diffusion of the BFM during the brazing process. It has been found that the diffusion process resulted in an increase in the rigidity of the porous Ni. The compressive strength tests for the brazed joint showed that the maximum compressive strength can be achieved for brazing at 680°C. The highest compressive strength value has been justified by quantitative analysis of the microstructural data. It has been proved that the VZ2250 BFM effectively diffused into the porous Ni at the brazing temperature of 680°C; Cu₃P and Cu₆Sn₅ were detected at the brazed Interface 1, whereas MnNi₃ phase at the brazed Interface 2.