| Résumé | Composite TiC-Fe coatings obtained by the plasma spray synthesis process can be composed of alternate TiC-rich and TiC-poor lamellae of different hardnesses. This study was undertaken to assess the influence of the fabrication parameters on the microstructure of these coatings. Both the composition of the micropellets, which lead to the synthesis and dispersion of fine crystals within the iron matrix upon spraying, and the spraying parameters were examined.
Among all the variables considered it was found that the parameters related to the fabrication of micropellets, such as their size and their expected TiC volume content, and those related to the solidification of synthesized products are the main factors affecting the hardness of TiC-rich layers.
Coatings obtained by spraying micropellets comprising TiC and iron powders agglomerated together are composed of large angular and hard TiC particles embedded in a matrix whose hardness is between 300 and 500 kgf mm⁻². In contrast, plasma-spray-synthesized coatings are composed of alternate soft and hard layers whose hardness varies according to the fabrication parameters and is between 1000 and 1800 kgf mm⁻² for hard layers and between 300 and 600 kgf mm⁻² for soft ones.
These plasma-spray-synthesized TiC-Fe coatings, because of their multilayer and fine-grained multiphase microstructure, are expected to be more resistant to crack propagation and, consequently, to wear. |
|---|
