Quality of dissimilar welded particle-reinforced TRIP/TWIP steels generated by electron beam braze-welding

ZrO2-reinforced high alloy steels have a strong tendency for pore formation during thermal joining and are therefore considered as non-weldable. However, present investigations have shown that it is possible to join particle-reinforced steels by a dissimilar electron beam braze-welding with a beam offset. The joints were characterised by light optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods, such as electron backscatter diffraction (EBSD), energy dispersive X-ray spectroscopy (EDS) and selected area electron diffraction (SAED). The mechanical properties and the deformation behaviour of the welded material were studied in tensile tests. The quality and type of the joints depend on the dilution of the weld. The welds with a level of dilution between 2 and 10% are free of defects and show an epitaxial growth onto the base material which yields superior mechanical properties compared to the welds without dilution. The welds produced by electron beam brazing exhibited the formation of oxide films which prevented an epitaxial growth of the solidified material. Therefore, a significant impact on the results of the tensile tests was noticed.