Plasma Spray Deposition of Lanthanum Phosphate and Phase Structure of the Resultant Coatings

摘要

Plasma-sprayed lanthanum phosphate coatings were prepared on stainless steel substrates at different input powers from 16 to 24 kW. Coatings were characterized by x-ray diffraction, scanning electron microscopy, and Fourier transformed infrared spectroscopy. Results showed that the as-sprayed coatings consist of lanthanum ortho (LaPO4), poly(La2P4O13), and oxy(La3PO7) phosphates. Subsequent heat treatment of the coatings resulted in the recombination of the La-polyphosphate and La-oxyphosphate to form LaPO4. SEM images of microstructure of the coatings and coating-substrate interface showed micro-cracks, voids, and porosity that were found to decrease with deposition power.