A Perspective on Thermally Sprayed Thermal Barrier Coatings: Current Status and Trends

Abstract

For more than 6 decades, thermal barrier coatings have been used to protect structural parts in both stationary and aviation gas turbines. These coatings allow the use of significant higher operation temperatures and hence increased efficiencies. In the 1970s, yttria-stabilized zirconia (YSZ) was identified as outstanding material for this application. As major deposition technologies both electron beam physical vapor deposition (EB-PVD) and atmospheric plasma spraying (APS) have been established. Although the topic is already rather old, there are still frequent activities ongoing to further improve the technology, both with respect to materials and microstructural issues also regarding the use of advanced coating technologies, especially in the field of thermal spray. The paper tries to summarize major developments in both fields, the materials and the processing focusing on thermal spray methods. The impact of both materials and processing are summarized by the results of burner rig tests for various systems. Furthermore, a short outlook on possible future directions of developments will be given.

Additive Manufacturing of Columnar Thermal Barrier Coatings by Laser Cladding of Ceramic Feedstock

“…All cited TBC sample tests are performed on the same burner rig facility with 5 min dwell time at high temperature and the surface temperatures of ≈1400 °C, except commercial EB‐PVD coatings with ceramic layer thicknesses well below 300 µm. [ 19 ]…”

“…Data for double layer top coat TBC samples with columnar SPS top coat layer (square symbols), single layer porous APS coatings (black line), typical range of results for commercial EB‐PVD TBCs (blue shading), and columnar single layer PS‐PVD coatings (diamond symbols). [ 19 ]…”

“…All cited TBC sample tests are performed on the same burner rig facility with 5 min dwell time at high temperature and the surface temperatures of ≈1400 °C, except commercial EB-PVD coatings with ceramic layer thicknesses well below 300 µm. [19] The Arrhenius type correlation is obvious in the logarithmic plot (Figure 6). The correlation is due to the thermally activated 2).…”

“…Data for double layer top coat TBC samples with columnar SPS top coat layer (square symbols), single layer porous APS coatings (black line), typical range of results for commercial EB-PVD TBCs (blue shading), and columnar single layer PS-PVD coatings (diamond symbols). [19] Sample Preparation: The substrates for the laser cladding of the YSZ columns were YSZ-coated steel plates. Porous YSZ coatings on steel were manufactured by atmospheric plasma spraying using a MultiCoat facility (Oerlikon Metco, Wohlen, Switzerland) with a three-cathode TriplexPro 210 gun.…”

Optimization of plasma spray process variables to attain the minimum porosity and maximum hardness of the LZ/YSZ thermal barrier coatings utilizing the response surface approach

“…Simply, the TBC system consists of at least three parts, namely, plasma-sprayed zirconia-based top layer coating, NiCrAlY superalloy-based intermediate bond layer, and substrate. The thermal barrier coating is bonded to the superalloy via a bond coat and substrate [2].…”