Abstract:
The application of cobalt and aluminium powders in unconstrained format, not as metal
powder in tubular wire nor as pre-alloyed powder, is used in this work to simplify weld metal
alloying. The objective of this study is to demonstrate the application of unconstrained cobalt and
aluminium powders in Submerged Arc Welding SAW to alloy the weld metal and to control the weld
metal oxygen content. Aluminium powder is used to control the oxygen potential at the weld poolslag
interface in order to prevent oxidation of cobalt. The results presented here show that with the
addition of Aluminium powder, 70% yield of Cobalt was achieved from the cobalt powder to the weld
metal. The carbon steel base-plate material and weld wire materials combination were alloyed to 5.3%
Co and 4.2% Al, whilst controlling the weld metal total oxygen content to 230 ppm. Thermodynamic
analysis is applied to investigate the possible chemical interaction reactions between Co and Al
compounds, as well as the role of the reactions on Co yield to the weld pool. The application of
unconstrained metal powders ensures productivity gains in the overall SAW process because the
time consuming and expensive manufacturing of alloyed wire and alloyed powder are eliminated.
