Application of Nickel Nanoparticles in Diffusion Bonding of Stainless Steel Surfaces

In this study, the effect of nickel nanoparticles (NiNPs) interlayer application to transient liquid-phase diffusion brazing was investigated. The primary focus was to bond stainless steel 316L laminae in a stack using a Nickel nanoparticles interlayer and to compare the bond line of the sample with the conventionally bonded and nickel-phosphorous interlayer (NiP) brazed samples for microstructure evolution and bond strength. The bonding was carried out in a vacuum hot press and the bonding parameters were kept same for all the samples: bonding temperatures 1000°C, bonding pressure 1000 psi, heating rate 10°C/min and dwell time of 2 hrs. The cross sections of the bonded samples were investigated for microstructure evolution using optical microscopy and scanning electron microscopy (SEM). The inter-diffusion of the diffusing species across the bond line (interface) was evaluated by wavelength dispersive spectroscopy (WDS). X-ray diffraction technique (XRD) is proposed to determine the formation of any brittle intermetallic phases along the bond line and transmission electron microscopy (TEM) to confirm the same. Bond strength will be measured with the help of samples bonded according to ASTM standards.