Strain-Induced Phase Transformation of MCrAlY

There is an increasing interest in cold spraying, which is commonly characterized as a solid-state deposition process offering minimal structural changes. The present paper refutes this common perception by examining the structural changes in MCrAlY as induced by cold spraying (CS). The cold-sprayed coatings were characterized for phase composition and microstructural features using X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. These results are compared with those obtained from the feedstock powder, as well as those obtained from ball-milled powder. An extensive phase transition from bcc to fcc is observed after both CS and after ball milling. In CS, in addition, there is evidence for substantial grain refinement, which is not observed after ball milling.