Electron beam freeforming on type 321 stainless steel using BNi-2 brazing paste

The use of electron beam technology for freeforming nickel based buildups on type 321 stainless steel substrates was investigated in the present work by using BNi-2 brazing paste as a filler metal. The electron beam freeforming studies involved variation of processing parameters, namely welding speed and number of successive melting passes, to examine the effect of these on the characteristics of the line buildups. It was determined that the amount of porosity in the deposited layers could be reduced to less than 0.6% by applying consecutive remelting passes and/or reducing the welding speed from 20 to 15 cm min⁻¹ without thermal softening of the buildups, as indicated by the high hardness of the rebuild. Nonetheless, since the dimensional features (height/width ratio) of the buildups were found to be dependent on both the number of remelting passes and the welding speed, tailoring of deposit quality in relation to geometrical requirements is necessary.