Distribution and transport of yttrium in alumina scales on iron-base ODS alloys

Optimal conditions for alumina coating formation on the MA956 superalloy for prosthetic bearing applications

“…This second diffusion process could explain the divergence of the layer thickness growth rate from the growth rate behavior of a unique diffusion process. [15][16][17] …”

“…[13][14][15] Though this oxidation process consists mainly of inward oxygen diffusion through the layer, this deviation of the parabolic behavior can be attributed to an increase in the oxide grain size near the oxide-metal substrate interface, which diminishes the diffusion path density in the alumina layer, 13,14 and to the cat- ionic diffusion processes from the base metal to the surface. 15,16 As mentioned earlier, layer thickness and alumina stability are the main factors to be considered for achieving an adequate chemical and biological protection of the metallic alloy as well as a satisfactory wear resistance. In Figure 2, several thickness isovalue curves can be distinguished.…”

Comment on “Oxidation of alloys containing aluminum and diffusion in Al2O3” [J. Appl. Phys. 95, 3217 (2004)]

“…However, undoped scales have been found to grow by a combination of Al and O boundary transport. [13][14][15][16][17][18] For comparison, a value was also calculated using the extrapolated lattice diffusion value. 21 As has been found for other oxides, 20 the calculated value was much lower than the measured values; as lattice transport is too slow to account for oxidation.…”

“…In undoped ␣-Al 2 O 3 , growth occurs by the combined grain-boundary transport of Al and O ions. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] With a RE addition to the substrate ͑e.g., Y, Zr, and Hf͒, whose ions segregate to the scale grain boundaries, the transport of Al is retarded and growth occurs predominantly by the grain boundary diffusion of O ions. 31 The newly proposed mechanism is not consistent with experimental evidence and, therefore, cannot be correct.…”

Corrosão de aços inoxidáveis avançados em meios fisiológicos

“…Os ensaios de XPS mostram ainda alguns indícios de óxido de alumínio e ausência de titânio ou ítrio. Por outro lado, a literatura (Ramanarayan et al, 1984, Versaci et al, 1993, Escudero e González-Carrasco, 1994, López et al, 1998, Czyrska-Filemonowicz et al, 1999, Pérez et al, 2001) relata que a camada de óxido formada em temperaturas acima de 800 ºC na superfície da Incoloy MA 956 é constituída de alumina compacta, aderente e densa, com teores de óxidos de Ti, Y, Cr e Fe presentes em forma de nódulos. Quadakkers et al (1992) acrescentam que a taxa de crescimento do óxido é influenciada pela presença de óxido de ítrio, que favorece a difusão do oxigênio.…”