TY - JOUR
T1 - Effects of Sintering Aides on the Hydrothermal Oxidation of Silicon Nitride Spherical Rolling Elements
AU - Bateman, Allyssa
AU - Queale, Abby J.
AU - Butt, Darryl P.
AU - Jaques, Brian J.
N1 - Publisher Copyright:
© 2018, © 2018 Institute of Materials, Minerals and Mining Published by Taylor & Francis on behalf of the Institute.
PY - 2019/2
Y1 - 2019/2
N2 - Commercially available silicon nitride (Si3N4) spherical bearing rolling elements containing TiO2, Y2O3, MgO and Al2O3 additives were evaluated for corrosion-resistance in high-temperature, high-pressure hydrothermal tests designed to simulate aero propulsion conditions. Spheres were exposed in an autoclave at 523–623 K and 5.2–16.5 MPa for 12–48 h and characterised using mass change and pH measurements, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy and inductively coupled plasma mass spectrometry. The oxidation resistance of the TiO2/Y2O3/Al2O3-sinter-aided Si3N4 ceramic closely matches the Y2O3/Al2O3-doped Si3N4 and outperforms the MgO-sinter-aided Si3N4. Additional studies on the TiO2/Y2O3/Al2O3 Si3N4 composition show pitting initiates around titanium-rich inclusions, due to a break in the protective hydroxide layer, accessible diffusion paths around inclusions and the catalytic nature of titanium. This study demonstrates that the addition of TiO2/Y2O3/Al2O3 to hot pressed Si3N4 reduces corrosion rates in high-temperature, high-pressure, hydrothermal environments.
AB - Commercially available silicon nitride (Si3N4) spherical bearing rolling elements containing TiO2, Y2O3, MgO and Al2O3 additives were evaluated for corrosion-resistance in high-temperature, high-pressure hydrothermal tests designed to simulate aero propulsion conditions. Spheres were exposed in an autoclave at 523–623 K and 5.2–16.5 MPa for 12–48 h and characterised using mass change and pH measurements, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy and inductively coupled plasma mass spectrometry. The oxidation resistance of the TiO2/Y2O3/Al2O3-sinter-aided Si3N4 ceramic closely matches the Y2O3/Al2O3-doped Si3N4 and outperforms the MgO-sinter-aided Si3N4. Additional studies on the TiO2/Y2O3/Al2O3 Si3N4 composition show pitting initiates around titanium-rich inclusions, due to a break in the protective hydroxide layer, accessible diffusion paths around inclusions and the catalytic nature of titanium. This study demonstrates that the addition of TiO2/Y2O3/Al2O3 to hot pressed Si3N4 reduces corrosion rates in high-temperature, high-pressure, hydrothermal environments.
KW - electron microscopy
KW - engineering ceramics
KW - high temperature
KW - hydrothermal
KW - sintering aides
KW - surface analysis
UR - http://www.scopus.com/inward/record.url?scp=85053782981&partnerID=8YFLogxK
UR - https://scholarworks.boisestate.edu/mse_facpubs/389
U2 - 10.1080/1478422X.2018.1523290
DO - 10.1080/1478422X.2018.1523290
M3 - Article
SN - 1478-422X
VL - 54
SP - 22
EP - 27
JO - Corrosion Engineering Science and Technology
JF - Corrosion Engineering Science and Technology
IS - 1
ER -