Effect of Processing Parameters on the Creep Behavior and Integrity of Plasma-Sprayed Thermal Barrier Coatings on Ti-6Al-4V.

This study investigates how processing parameters and powder characteristics influence the mechanical performance of thermal barrier coatings (TBCs) applied to a Ti-6Al-4V alloy. Two TBCs were deposited by Atmospheric Plasma Spray (APS) using different processing conditions, feedstock characteristics, and coating thicknesses (thin and thick configurations). TBC characterization included powder size analysis, scanning electron microscopy (SEM), surface roughness, X-ray diffraction, instrumented indentation, and scratch testing. Mechanical behavior was assessed using creep testing at 125 MPa and 500 °C for coated and uncoated samples. Fracture surfaces of crept samples were analyzed by SEM and stereomicroscopy. Thicker TBC exhibited higher elastic modulus but contained microcracks and higher porosity, resulting in a higher steady-state creep rate (0.0006 h-1, approximately 167% above the uncoated substrate) and reduced rupture time. Conversely, thinner TBC remained initially crack-free, promoting stress redistribution and leading to a lower creep rate (0.0002 h-1, about 67% below the substrate) and delayed failure. Fractographic analysis revealed ductile fracture of Ti-6Al-4V in all conditions, indicating that coatings influenced damage accumulation rather than fracture mode. These findings underscore the combined effect of processing parameters and coating architecture on TBC performance for aerospace applications.