Microstructure and stresses in HVOF sprayed iron aluminide coatings

摘要

The microstructure and state of stress present in Fe{sub}3Al coatings produced by high velocity oxygen fuel (HVOF) thermal spraying in air at varying particle velocities were characterized using metallography, curvature measurements, X-ray analysis, and microhardness measurements. Sound coatings were produced for all conditions. The microstructures of coatings prepared at higher velocities showed fewer unmelted particles and a greater extent of deformation. Residual stresses in the coatings were compressive and varied from nearly zero at the lowest velocity to approximately -450 MPa at the highest velocity. X-ray line broadening analyses revealed a corresponding increase in the extent of cold work present in the coating, which was also reflected in increased microhardness. Values of mean coefficient of thermal expansion obtained for as-sprayed coatings using X-ray analysis were significantly lower than those for powder and bulk alloy.