scholarly journals Effect of particle size of Y2O3-Al2O3 additives on microstructure and mechanical properties of Si3N4 ceramic balls for bearing applications

2021 ◽  
Vol 15 (3) ◽  
pp. 297-305
Author(s):  
Jing Zhang ◽  
Wenxue Wang ◽  
Feng Sun ◽  
Weiru Zhang ◽  
Boheng Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Particle Size ◽  
Relative Density ◽  
Si3n4 Ceramic ◽  
Sintering Additives ◽  
Microstructure And Mechanical Properties ◽  
Indentation Fracture Toughness ◽  
Effect Of Particle Size ◽  
Gas Pressure Sintering ◽  
Si3n4 Matrix

Si3N4 ceramic balls were prepared by gas pressure sintering with Y2O3 and Al2O3 as sintering additives. The effects of particle size of Y2O3-Al2O3 additives on densification, microstructure and mechanical properties of Si3N4 ceramic balls were investigated. The reliability of Si3N4 ceramic balls was evaluated through the Weibull modulus. The results showed that Si3N4 ceramic balls containing nanosized Y2O3-Al2O3 additives have a higher relative density and better comprehensivemechanical properties compared with the samples containing microsized additives, with relative density of 98.9 ? 0.2%TD, Vickers hardness of 14.7 ? 0.1GPa, indentation fracture toughness of 6.5 ? 0.1MPa?m1/2 and crushing strength of 254 ? 8.5MPa. The more homogeneous and extensive dispersion of the nanosized sintering additives in the Si3N4 matrix is the main reason for the enhancement in density and mechanical properties of the Si3N4 ceramic balls.

Effects of Sintering Additives on the Microstructure and Mechanical Properties of Silicon Nitride Ceramics by GPS

2010 ◽  
Vol 105-106 ◽  
pp. 27-30 ◽  
Author(s):  
Wei Ru Zhang ◽  
Feng Sun ◽  
Ting Yan Tian ◽  
Xiang Hong Teng ◽  
Min Chao Ru ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Phase Transformation ◽  
Silicon Nitride ◽  
Porous Silicon ◽  
Flexural Strength ◽  
Relative Density ◽  
Sintering Additives ◽  
Microstructure And Mechanical Properties ◽  
Nitride Ceramics

Silicon nitride ceramics were prepared by gas pressure sintering (GPS) with different sintering additives, including La2O3, Sm2O3 and Al2O3. Effect of sintering additives on the phase-transformation, microstructure and mechanical properties of porous silicon nitride ceramics was investigated. The results show that the reaction of sintering additives each other and with SiO2 had key effects on the phase-transformation, grain growing and grain boundaries. With 9MPa N2 atmosphere pressure, holding 1h at 1850°C, adding 10wt% one of the La2O3, Sm2O3, Al2O3, porous silicon nitride was prepared and the relative density was 78%, 72%, 85% respectively. The flexural strength was less than 500MPa, and the fracture toughness was less than 4.8MPam1/2. Dropping compounds sintering additives, such as La2O3+Al2O3, Sm2O3+Al2O3 effectively improves the sintering and mechanical properties. The relative density was 99.2% and 98.7% with 10wt% compounds sintering additives. The grain ratio of length to diameter was up to 1:8. The flexural strength was more than 900MPa, and the fracture toughness was more than 8.9MPam1/2.

Effect of Particle Size and Vacuum Sintering Temperature on Phase Composition and Mechanical Properties of WC-12 wt% Co Hardmetals

2012 ◽  
Vol 531-532 ◽  
pp. 3-7
Author(s):  
Shih Hsien Chang ◽  
Chung Wei Lee ◽  
Kuo Tsung Huang ◽  
Ming Wei Wu
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Particle Size ◽  
Relative Density ◽  
Sintering Temperature ◽  
Liquid Phase Sintering ◽  
Sintering Process ◽  
Vacuum Sintering ◽  
Brittle Phase ◽  
Effect Of Particle Size

The experimental results indicated that the WC-12wt% Co specimens showed excellent mechanical properties and microstructure by the optimal sintering process. The G5 specimen sintered at 1400°C/1 h achieved a relative density of 98% and a hardness of HRA 88.5. Meanwhile, the TRS increased to 2400 MPa. F12 specimens that sintered at 1350°C/1 h achieved a relative density of 99% and a hardness of HRA 92.5. The TRS was also enhanced to 2170 MPa. In this study, the η phase (Co3W3C) precipitated at a high sintering temperature. The precipitations generated by liquid phase sintering gathered in some specific regions of the specimens and reacted with the WC particles. In addition, Co3W3C was a hard and brittle phase that resulted in a low TRS for the specimens; and a large amount of η phases were detrimental to the fracture toughness of the specimens.

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