Influence of porosity on thermal properties of columnar suspension plasma sprayed thermal barrier coatings

Suspension Plasma Spraying is a relatively new thermal spaying technique to produce advanced thermal barrier coatings. This technique enables the production of a variety of structures from highly dense, highly porous, segmented or columnar coatings. In this work a comparative study is performed on six different suspension plasma sprayed coatings which were produced using axial injection and different process parameters. The influence of coating morphology and porosity on thermal properties was of specific interest. Tests carried out include microstructural analysis with SEM, porosity analysis using Archimedes experimental setup, mercury infiltration technique and thermal conductivity measurements using laser flash analysis. The samples were also heat treated at 1150°C for 200 and 400 hours. The results showed that high performance coatings were produced using relatively high feed rates and spray distances. Heat treatment did not dramatically increased thermal conductivity for all the samples.