Effect of temperature rise of sprayed deposits of an Fe-2.19wt.%C-0.68wt.%Si alloy during thermal spraying on the structures and the mechanical properties

Powder of an Fe-2.19wt.%C-0.68wt.%Si alloy was low pressure plasma sprayed onto substrates which were cooled to various extents. The deposit held at low temperatures during spraying consisted predominantly of retained austenite supersaturated with carbon. The strength of the deposit, measured on tensile test pieces machined from the deposit, was low. When the deposit temperature was allowed to rise during spraying owing to heat from the plasma flame, the constituents of the deposit were ferrite, cementite and, in some cases, graphite. With increasing maximum temperature of the deposit, the adhesion between the lamellae composing the deposit became stronger, the porosity decreased, the cementite precipitates became coarser and, at higher temperatures, graphite precipitated. Owing to the combined effects of all these structural changes, the strength reached a maximum value of 1.34 GPa when the deposit temperature was slightly raised during spraying.