In situ synchrotron investigation of tensile deformation and failure mechanisms in cold spray Cr-coated Zr-alloy system

Abstract

High energy synchrotron X-ray diffraction in the transmission mode was performed in situ during uniaxial tensile testing to understand the deformation and cracking behavior of cold spray Cr-coated Zr-alloy specimens in both the as-deposited and annealed conditions. The fracture surface of the specimens, examined using scanning electron microscopy, revealed that the Cr coatings in both samples remained strongly adherent to the substrates through the completion of the tensile test. Both elastic and plastic deformation mechanisms during tensile deformation were quantified using detailed X-ray line profile analysis. High dislocation density with a unique distribution of edge and screw fractions and non-zero lattice strain was determined to be present in the cold spray Cr coating due to high strain-rate deformation during cold spray deposition. The annealing treatment reduced both residual lattice strain and dislocation density (with preferentially higher reduction in edge fractions) in the Cr coating. This led to a heterogeneous distribution of dislocation density and character among different grains, that enhanced resistance to crack propagation in the annealed Cr coating. The mechanical properties of the Zr-alloy in both specimens were not significantly altered by the presence of the cold sprayed Cr coating on the surface.

Keywords

• Cold spray
• Cr coated Zr-alloy
• In situ tensile investigation
• Synchrotron diffraction
• Dislocation density evolution