Foreign Object Damage (FOD) in Thermal Barrier Coatings

Phenomena of Foreign Object Damage by Spherical Projectiles in EB-PVD Thermal Barrier Coatings of Turbine Airfoils

“…4) obtained from the vane airfoils in this study were in a stark contrast to those of the EB-PVD FfPT blades in the previous study, particularly at higher impact velocities [11,12], The previous FOD work on those F1PT blades showed that, at a low impact velocity of 150 m/s, the impact damage was simply impressions, similar to those observed in the current study, while at V > 200 m/s, a significant morphological change occurred from mere impressions to substantial spallation, as shown in Fig. 5 [11,12], Most of the spallations of the blade TBCs at 300 m/s took place along the topcoat and bondcoat interfaces (TGO). There might be several reasons for the outcome of such a significant dif ference in FOD between the vane and the blade airfoils.…”

“…Because of limited availability of the airfoil components, only two vanes were used in the experiments. Rela tively large flat areas of TBCs in the hardware, compared to the HPT blades used in the previous work [11][12][13], enabled to cover all the test matrices intended. Impact Morphologies.…”

“…A series of FOD work has been conducted previously using a number of actual airfoils (high-pressure turbine (HPT) blades) coated with 110 mn-thick EB-PVD TBCs (7YSZ) [11][12][13], The airfoil components were used as targets and were subject to ballis tic impact in a range of velocities up to Mach 1 by 1.6-mm spheri cal ball projectiles of hardened chrome steel, silicon nitride, and borosilicate glass. The impact damage was assessed in terms of impact velocity, projectile material, and remaining life of turbine components.…”

“…The vane airfoils were impacted using similar test condi tions that were applied to the HPT blades [11][12][13] but employing only one projectile material, hardened chrome steel. Assessments of the thick TBCs in response to FOD were made from the impact sites as well as from the cross sections, and their behavior was compared with that of the thin (110 /<m) EB-PVD HPT blades.…”

“…A ballistic impact gun, as described elsewhere [11][12][13][14][15], was used to carry out FOD testing for the EB-PVD TBC-coated vane airfoils. The projectiles used in the testing were commercial, 1.6-mm-diameter spheres of hardened chrome bearing steel (grade 5), and their basic physical and mechanical properties are presented in Table 1.…”