Thermal Stability of Nanostructured Cr₃C₂-NiCr Coatings

Characterisation of HVOF sprayed Cr3C2-50(Ni20Cr) coating and the influence of binder properties on solid particle erosion behaviour

“…Upon impact with a relatively cooler substrate these small particles are rapidly cooled and solidified with the binder supersaturated with Cr and C [10,12]. This results in a coating that has a metastable microstructure which upon annealing transforms to a more stable microstructure [3,[10][11][12][13][14][15].…”

“…They are now increasingly being deposited by high velocity spray processes like high velocity oxy-fuel (HVOF), detonation gun spray and high velocity air-fuel (HVAF) processes to minimize decarburisation of carbides during the spray process and to produce dense coatings [3,[5][6][7][8] resulting in an improved wear performance. Thermal spraying of Cr 3 C 2 -NiCr powder causes dissolution of some carbide particles in-flight increasing the Cr and C content in the molten NiCr binder [7,[9][10][11][12][13][14][15][16][17]. Upon impact with a relatively cooler substrate these small particles are rapidly cooled and solidified with the binder supersaturated with Cr and C [10,12].…”

“…The dissolution of carbide in the binder during thermal spraying significantly influences the coating microstructural stability [10][11][12][13][14][15][16]. Heat treatment of these coatings causes precipitation of secondary carbides within the supersaturated binder increasing the effective carbide volume fraction with the consequential change in the binder composition and microstructure [10][11][12][13][14][15][16][18][19][20].…”

The spray forming of nanostructured Aluminum Oxide

“…13 Due to the higher thermal conductivity of Al 2 O 3 , the outside of the particle gets superheated and effectively conducts the heat to the core to cause melting. Hence, it could be concluded that in the absence of TiO 2 , a lower value of IV/Ar ratio would result in a relatively higher degree of melting in pure Al 2 …”

“…For example, plasma spraying has been investigated by several researchers to deposit nanostructured ceramic coatings such as WC, Cr 3 C 2 , Al 2 O 3 -TiO 2 , and ZrO 2 . [1][2][3][4][5][6] However, the use of plasma spraying to fabricate a bulk, freestanding nanostructured Al 2 O 3 component has rarely been reported in the literature. In this study, freestanding, net-shape nanostructured Al 2 O 3 structures were fabricated using plasma-spray forming.…”