Thermal Barrier Coatings Made by the Solution Precursor Plasma Spray Process

Abstract

The solution precursor plasma spray (SPPS) process is a relatively new and flexible thermal spray process that can produce a wide variety of novel materials, including some with superior properties. The SPPS process involves injecting atomized droplets of a precursor solution into the plasma. The properties of resultant deposits depend on the time-temperature history of the droplets in the plasma, ranging from ultra-fine splats to unmelted crystalline particles to unpyrolized particles. By controlling the volume fraction of these three different constituents, a variety of coatings can be produced, all with a nanograin size. In this article, we will be reviewing research related to thermal barrier coatings, emphasizing the processing conditions necessary to obtain a range of microstructures and associated properties. The SPPS process produces a unique strain-tolerant, low-thermal conductivity microstructure consisting of (i) three-dimensional micrometer and nanometer pores, (ii) through-coating thickness (vertical) cracks, (iii) ultra-fine splats, and (iv) inter-pass boundaries. Both thin (0.12 mm) and thick (4 mm) coatings have been fabricated. The volume fraction of porosity can be varied from 10% to 40% while retaining the characteristic microstructure of vertical cracks and ultra-fine splats. The mechanism of vertical crack formation will be described.

Solution and Suspension Plasma Spraying of Nanostructure Coatings

“…www.intechopen.com Gell et al (2008) studied the properties and resistance to thermal shock test of YSZ coatings made by solution precursor plasma spraying. They tested various atomization systems to inject the solution in the plasma jet.…”

“…b. Features of solution plasma-sprayed TBCs using an air blast atomizer, details including vertical cracks, dense regions of ultra-fine splats, small and uniformly dispersed porosity, un-melted particles Gell et al (2008).…”

Parameters Controlling Liquid Plasma Spraying: Solutions, Sols, or Suspensions

“…It has been used for suspensions and solutions ( Ref 1,11,30,[47][48][49][50][51]. Very often co-axial atomization is used.…”

Thermal and mechanical properties of crack-designed thick lanthanum zirconate coatings

“…Recently, solution precursor plasma spray (SPPS) technique was developed to take advantage of using a liquid precursor as feedstock to deposit nanostructured coatings [15]. A typical coating deposited by SPPS consists of ultra-fine splats, through thickness vertical cracks, embedded un-pyrolized particles, and uniformly dispersed nanopores, which generate coatings with low thermal conductivity and improved durability [16].…”