A study on the effect of variation of aluminide coating thickness on the tensile deformation behavior of a near-α titanium alloy using infrared thermography

Coatings are applied to titanium alloys to prolong the life of the components by improving the high temperature oxidation and corrosion resistance. The coating thickness needs to be optimized depending upon the service conditions. The coating thickness can potentially affect the mechanical properties of the substrate alloy. In the present study, the effect of variation in the coating thickness on the deformation behavior of a near-α titanium alloy coated with Al3Ti aluminide has been studied. Infrared thermography technique has been used to monitor the local heat evolution along the gauge portion of uncoated and coated specimens during tensile deformation. The technique has been used to measure the dissipated heat and to monitor the changes in the stored energy during tensile deformation. The presence of coating led to only marginal variations in strength although it reduced the alloy ductility significantly. The coated specimens failed by propagation of cracks from the coating to the substrate material. It is observed that several cracks penetrate into the substrate alloy and the unstable propagation of these cracks led to failure of the specimen. This study also shows that the localized heat evolution during the crack propagation process can be effectively used as a parameter for studying the in-homogeneous deformation and fracture process typical in coated materials.