ANALYTICAL TRANSMISSION ELECTRON-MICROSCOPY CHARACTERIZATION OF PLASMA SPRAY SYNTHESIZED TIB2-FE COATINGS

Cermet coatings containing TiB2 crystals dispersed in an iron-based matrix have been obtained by the plasma spray synthesis process developed at the Industrial Materials Research Institute. The main feature of this technique is the combination in a one-step operation of both the synthesis and the deposition process. The resultant coatings are thick and possess a good abrasion resistance. In order to elucidate the fine microstructure of these TiB2-Fe coatings obtained through a rapid solidification process and to understand their good abrasion-wear behavior, a transmission electron microscopy study has been undertaken. Energy-dispersive spectroscopy using an ultrathin window detector and electron energy loss spectroscopy (EELS) techniques, both allowing the detection of relatively light elements, were used. For the range of compositions investigated, EELS was more sensitive for the localization of boron and offered a better spatial resolution. The results have shown that coatings obtained by the plasma spray synthesis process contain TiB2 particles ranging from 10 to 700 nm in size dispersed in a matrix of iron and FeTi. The unusual microstructure of these coatings is probably responsible for their good wear resistance.