The Study Of Joint Brazed With Ni-P Interlay And Its Diffusing Behaviour For A Stainless Steel

An amorphous Ni- P ribbon was prepared as interlayer for bonding of a stainless steel. The microstructure and melting behaviour of amorphous ribbons were investigated by DTA, XRD, EPMA. The bonding process for stainless steel with amorphous Ni- P interlayer were studied by many means.The results indicated that the melting temperature of amorphous brazing foils are lower about 5℃ than as-cast filler metal. The Crystallization interval of amorphous foils is narrow about 4℃ than as-cast filler metal. The mechanics strength of joint with amorphous foils are better than as-cast filler metal.The joining areas is made of three parts, a brittle phase in middle area, white Ni solid solution and element diffuse area. The brittle phase is Ni₂P and Ni₃P. As holding time increasing, the average brittle thickness is decrease. On increasing the holding time at the bonding temperatures there was a considerable reduction in the width of the brittle phase and joint area. There are a lot of Ni atoms to diffuse from filler metal and tiny phosphor atoms in base metal. A lot of phosphor atoms stay in joint middle area and form Ni₂P and Ni₃P.On increasing the joint gap, the Ni solid solution at interface is decrease and the brittle phase increased, which lead to the tensile strength decreases rapidly. With soldering pressure increasing Ni solid solution atinterface reaction zone is increasing and the brittle phase decreasing.Comparing with the diffusing capacity of different atoms, it could be found nickel atom is best ,than iron and chrome atoms, and phosphor atom.