Solution Precursor Plasma Spray Applied to Thermal Barrier Coatings

Abstract- Solution precursor plasma spray (SPPS) is performed by injecting liquid chemical precursors into an atmospheric pressure plasma torch jet to form a thermal spray coating in a single step.  This process is particularly suitable for thermal barrier coating (TBC) production, in part because it is easy to make porous coatings with stress relieving through-coating-thickness cracks. Another advantage is the ability to quickly develop new compositions due the simple mixing of suitable solution precursors.   In this presentation, we will first review past SPPS TBC research and then discuss some new results.  Past results include a discussion of the through-thickness-crack formation mechanism and the resultant ability to form thick, durable TBCs. Emphasis will also be placed on the capability of the SPPS process to form layered porosity and thereby lower the thermal conductivity of TBCs.    New results will include presentation of a SPPS gadolinium zirconate TBC, the production of a surprisingly durable temperature sensing thermographic layer, the achievement of a new higher rate of deposition for the process (90 ml/minute equivalent to approximately 3 lbs/hour) and finally the prospect for even higher deposition rates thought the use of organic precursors that require less energy to process.