Neutron imaging: A non-destructive testing method for brazed components using boron alloyed nickel braze filler

摘要

Since decades high stressed components of stainless steel and nickel alloys have been brazed with nickel filler. Applications are in gas turbines and jet engines. Other applications can be found in space, aeronautic, automotive e.g.. High quality brazing seams have the same high mechanical strength as weld seams. So nickel brazing using borated filler is today an established process to join high stressed parts. One of the problems with brazing stainless steel, nickel alloys e.g. with nickel braze fillers is the limitation in non-destructive testing, (NDT), as for X-ray, the contrast of the filler material does not differ much from the base material. Here we introduce an imaging method based on thermal neutrons, which offers the possibility for NDT on braze seams of boron alloyed nickel braze filler. Experimental results with test samples, brazed with the boron alloyed nickel braze filler BNi-2 are presented. The samples were made of stainless steel, nickel alloys and copper. As boron is a strong neutron absorbing material and the base materials are rather transparent a pronounced contrast for the brazing seams is obtained. The presented results are radiographic images in 2D and tomographic reconstructions in 3D, both providing information of the filler distribution.