TY - JOUR
T1 - Effect of Y2O3 content on the microstructural characteristics and the mechanical and thermal properties of Yb-doped SiAlON ceramics
AU - Choi, Jae Hyeong
AU - Lee, Sung Min
AU - Nahm, Sahn
AU - Kim, Seongwon
N1 - Funding Information:
This work was supported by the Industrial Strategic Technology Development Program [grant number 10067065 ; Development of Coated Hard-metal/cBN/ceramic cutting Tools for Machining Heat-resistant Alloys with High Hardness, Utilized Innovation, and Energy Plant Industry] funded by the Ministry of Trade, Industry and Energy (MOTIE, Korea) , and the Korea Evaluation Institute of Industrial Technology (KEIT, Korea) .
Publisher Copyright:
© 2022
PY - 2022
Y1 - 2022
N2 - SiAlON ceramics are primarily employed in ceramic cutting tools, which exploit their stable physical properties in high-temperature cutting environments due to their excellent mechanical properties. Here, Yb/Y-co-doped SiAlON ceramics are prepared by adding Yb and Y rare-earth (RE) ions in the RExSi12-(m+n)Alm+nOnN16-n (m = 0.4, n = 1.0) composition. Yb2O3, the RE oxide, is the main sintering additive. For REx composition design with (Yb1-y + Yy)x, Yb2O3 is replaced by Y2O3 (y = 0.00, 0.25, 0.50, 0.75, 1.00). While Yb2O3 has excellent high-temperature stability, it is limited by its microstructural characteristics, that is, the β-SiAlON morphology and limited fracture toughness due to the small cation sizes. Thus, the changes in the above properties are investigated for various Y2O3 additive contents substituting for Yb2O3. The average grain width decreases, and the equiaxed β-SiAlON grains are elongated with increasing Y2O3 content. Regarding the mechanical properties, the hardness and fracture toughness are evaluated using the indentation fracture method. The hardness decreases with increasing Y2O3 content; however, the fracture toughness exhibits a significant increase (∼53.6%) from 4.6 to 7.0 MPa⋅m1/2. Regarding crack propagation, intergranular fracture is mainly observed in the Yb/Y-co-doped SiAlON ceramics, whereas transgranular fracture is primarily observed in the Yb-single-doped SiAlON ceramic. Y2O3 substitution increases the α/β-SiAlON phase ratio, and the grain boundary phase exhibits increasing vitrification with increasing Y2O3 content. Moreover, the thermal properties of the Yb/Y-co-doped compositions are analyzed and discussed regarding intrinsic properties such as phonon scattering. The microstructural characteristics and improved fracture toughness derived from the Yb/Y-co-doped system designed in this study suggest considerable potential for the future composition design of ceramic cutting tools.
AB - SiAlON ceramics are primarily employed in ceramic cutting tools, which exploit their stable physical properties in high-temperature cutting environments due to their excellent mechanical properties. Here, Yb/Y-co-doped SiAlON ceramics are prepared by adding Yb and Y rare-earth (RE) ions in the RExSi12-(m+n)Alm+nOnN16-n (m = 0.4, n = 1.0) composition. Yb2O3, the RE oxide, is the main sintering additive. For REx composition design with (Yb1-y + Yy)x, Yb2O3 is replaced by Y2O3 (y = 0.00, 0.25, 0.50, 0.75, 1.00). While Yb2O3 has excellent high-temperature stability, it is limited by its microstructural characteristics, that is, the β-SiAlON morphology and limited fracture toughness due to the small cation sizes. Thus, the changes in the above properties are investigated for various Y2O3 additive contents substituting for Yb2O3. The average grain width decreases, and the equiaxed β-SiAlON grains are elongated with increasing Y2O3 content. Regarding the mechanical properties, the hardness and fracture toughness are evaluated using the indentation fracture method. The hardness decreases with increasing Y2O3 content; however, the fracture toughness exhibits a significant increase (∼53.6%) from 4.6 to 7.0 MPa⋅m1/2. Regarding crack propagation, intergranular fracture is mainly observed in the Yb/Y-co-doped SiAlON ceramics, whereas transgranular fracture is primarily observed in the Yb-single-doped SiAlON ceramic. Y2O3 substitution increases the α/β-SiAlON phase ratio, and the grain boundary phase exhibits increasing vitrification with increasing Y2O3 content. Moreover, the thermal properties of the Yb/Y-co-doped compositions are analyzed and discussed regarding intrinsic properties such as phonon scattering. The microstructural characteristics and improved fracture toughness derived from the Yb/Y-co-doped system designed in this study suggest considerable potential for the future composition design of ceramic cutting tools.
KW - Mechanical properties
KW - Microstructure
KW - Thermal properties
KW - Yb/Y co-doping
UR - http://www.scopus.com/inward/record.url?scp=85122964675&partnerID=8YFLogxK
U2 - 10.1016/j.ceramint.2022.01.077
DO - 10.1016/j.ceramint.2022.01.077
M3 - Article
AN - SCOPUS:85122964675
SN - 0272-8842
JO - Ceramics International
JF - Ceramics International
ER -