Addition of Nano-ZrO2 Effects on Microstructures and Properties of WC-8Co Hard Alloys

2012 ◽  
Vol 496 ◽  
pp. 302-305 ◽  
Author(s):  
Lan Sun
Keyword(s):  
Mechanical Properties ◽  
Phase Transition ◽  
Fracture Toughness ◽  
Relative Density ◽  
Hard Alloys ◽  
Densification Behavior ◽  
Sintering Process ◽  
Toughening Mechanism ◽  
Hard Metals ◽  
Conventional Sintering

This paper carries out the research on using the toughening mechanism of phase transition of ZrO2 to inhibit the WC grain and improve the toughness of the hard alloys. WC–ZrO2–8wt%Co hard metals was mixed with 0-2 wt% nano-ZrO2 and prepared by conventional sintering (CS) for 2 h at 1440oC to see whether the addition of ZrO2 could improve densification behavior, the microstructure and mechanical properties of the samples. Experimental results showed that the use of ZrO2 nanoparticles could decrease the relative density because of the worse wetting effects; it could also inhibit the growth of the grains of WC-Co hardmetal to enhance the hardness of the alloy. The fracture toughness of sample has an increasing tendency as a whole because of the phase transition during the sintering process.

Fast Densification of B4C Ceramics with Al2O3 as a Sintering Aid by Spark Plasma Sintering

2009 ◽  
Vol 620-622 ◽  
pp. 395-398 ◽  
Author(s):  
Fan Zhang ◽  
Zheng Yi Fu ◽  
Jin Yong Zhang ◽  
Hao Wang ◽  
Wei Min Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Relative Density ◽  
Melting Temperature ◽  
Densification Behavior ◽  
Sintering Aid ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Enhanced Mobility ◽  
Mobility Of Elements

The densification behavior and mechanical properties of B4C by SPS at 1900°C for 2 min with additions of Al2O3 up to 10 wt.% were investigated. When the additional of 10 wt.%, the relative density was 99% and the hardness went to 33GPa. Sinterability was greatly improved by the addition of a small amount of Al2O3, and the SPS technology with high hearing rate is particularly attractive for prepare of poorly sinterable materials. The improvement was attributed to the enhanced mobility of elements through the Al2O3 near the melting temperature. As a result of this improvement in the density, mechanical properties, such as hardness, fracture toughness, increased remarkably.

Effects of Ti(C,N) Nanoparticles on Mechanical Properties of the Si3N4 Ceramics

2011 ◽  
Vol 80-81 ◽  
pp. 119-122
Author(s):  
Qian Li ◽  
Fu Sheng Zhu ◽  
Zhi Meng Xiu ◽  
Xu Dong Sun
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Aspect Ratio ◽  
Relative Density ◽  
Hot Pressing ◽  
Bending Strength ◽  
Lateral Growth ◽  
Toughening Mechanism ◽  
Vacuum Sintering ◽  
Crack Bridging

Si3N4-Ti(C,N) nanocomposites fabricated by vacuum hot pressing with Al2O3 and Y2O3 as additives were investigated. The results showed that the α-Si3N4 phase converted completely into whisker-shaped β-Si3N4 grains after vacuum sintering at 1700°C. Suitable addition and well dispersion of the Ti(C,N) particles can restrained the lateral growth of the β-Si3N4 grains, increasing aspect ratio of the β-Si3N4 grains and improving bending strength of the composites. Fracture toughness of the composites is higher than that of the β-Si3N4 ceramics, and the main toughening mechanism is crack bridging due to the higher aspect ratio of the β-Si3N4 grains.With the addition of 1vol% of Ti(C,N), the composite has a relative density of 99.31%, Vicker’s hardness of 15.9 GPa, bending strength of 993 MPa, and fracture toughness of 9.9 MPa·m1/2.

scholarly journals Densification and Mechanical Properties of Alumina Ceramics via Two-Step Sintering With Different Holding Times

2021 ◽  
Vol 6 (4) ◽  
pp. 299-304
Author(s):  
Anis Syufina Mohammad Saufi ◽  
Ramesh Singh ◽  
K. Y. Sara Lee ◽  
Tao Wu
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Grain Size ◽  
Relative Density ◽  
Grain Growth ◽  
Vickers Hardness ◽  
Holding Time ◽  
Alumina Ceramics ◽  
Conventional Sintering ◽  
Viable Approach

The densification and mechanical properties of alumina ceramics were investigated via two-step sintering (TSS) with different holding time. The alumina ceramics were sintered at 1450 °C for 1 min during the first stage, followed by sintering at 1350 °C with different holding times (2-24h). Conventional sintering (CS) was also performed on the alumina ceramics at 1450 °C for 2 h for comparison purpose. It was found that dense alumina with a relative density above 98% could be attained when TSS with a holding time of more than 12 h. The samples exhibited Vickers hardness between 5-8 GPa and fracture toughness of about 6 MPa.m1/2. In contrast, conventional sintered alumina yielded low relative density (85%), large grain size (2 μm), low Vickers hardness (4.23 GPa) and fracture toughness (4.73 MPa.m1/2). This study revealed that TSS is a viable approach in aiding densification, suppressing grain growth, and improving the mechanical properties of alumina ceramics.

Mechanical Properties of ZrB2-Based Ceramics Reinforced by Nano-SiC Whiskers

2007 ◽  
Vol 353-358 ◽  
pp. 1564-1567 ◽  
Author(s):  
Hai Long Wang ◽  
Chang An Wang ◽  
Rui Zhang ◽  
Xing Hu ◽  
Dai Ning Fang
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Grain Size ◽  
Relative Density ◽  
Hot Pressing ◽  
Bending Strength ◽  
Sintering Process ◽  
Homogeneous Microstructure ◽  
Sic Whiskers ◽  
Xrd Techniques

In this paper, ZrB2-based ceramics containing up to 15 vol% nano-SiC whiskers were prepared by hot pressing at 1950°C under 20MPa pressure in flow argon. SEM and XRD techniques were used to characterize the sintered compacts. A fine and homogeneous microstructure was observed. The relative density of ZrB2-based ceramic containing 10vol% SiC whiskers reached to 97.7%. The bending strength and fracture toughness of the composite were 550 MPa and 8.08 MPa·m1/2 respectively, while those of the monolithic ZrB2 ceramic (0 vol% SiC whiskers added) were 424 MPa and 4.52 MPa·m1/2 respectively. The grain size of the ZrB2-based ceramics was reduced greatly by the addition of nano-SiC whiskers during the sintering process.

Effect of B4C on the Mechanical Properties and Microstructure of ZrB2-SiC Based Ceramics

2010 ◽  
Vol 105-106 ◽  
pp. 218-221 ◽  
Author(s):  
Xuan Liu ◽  
Qiang Xu ◽  
Shi Zhen Zhu
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
High Temperature ◽  
Relative Density ◽  
Room Temperature ◽  
High Temperature Strength ◽  
Sintering Process ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Room Temperature Strength

ZrB2-SiC-B4C is sintered at 1700°C by spark plasma sintering process. The effect of B4C content on the mechanical properties and microstructure of ZrB2-SiC based ceramics is studied. The results show that, with the content of B4C increases, the relative density and room-temperature strength decrease in the ZrB2-SiC-B4C composite. The fracture toughness rises at first and then falls down. The high temperature strength increases.

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.

scholarly journals Improvement of mechanical properties of HfB2-based composites by incorporating in situ SiC reinforcement through pressureless sintering

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
S. Ghadami ◽  
E. Taheri-Nassaj ◽  
H. R. Baharvandi ◽  
F. Ghadami
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Relative Density ◽  
Pressureless Sintering ◽  
Sintering Process ◽  
Vacuum Atmosphere ◽  
Sic Reinforcement ◽  
Microstructural Studies ◽  
Composite Samples

AbstractHfB2, Si, and activated carbon powders were selected to fabricate 0–30 vol% SiC reinforced HfB2-based composite. Pressureless sintering process was performed at 2050 °C for 4 h under a vacuum atmosphere. Microstructural studies revealed that in situ SiC reinforcement was formed and distributed in the composite according to the following reaction: Si + C = SiC. A maximum relative density of 98% was measured for the 20 vol% SiC containing HfB2 composite. Mechanical investigations showed that the hardness and the fracture toughness of these composites were increased and reached up to 21.2 GPa for HfB2-30 vol% SiC and 4.9 MPa.m1/2 for HfB2-20 vol% SiC, respectively. Results showed that alpha-SiC reinforcements were created jagged, irregular, and elongated in shape which were in situ formed between HfB2 grains and filled the porosities. Formation of alpha-SiC contributed to improving the relative density and mechanical properties of the composite samples. By increasing SiC content, an enhanced trend of thermal conductivity was observed as well as a reduced trend for electrical conductivity.

Effect of Sintering Temperature on Microstructure and Mechanical Properties of Al2O3-TiC-ZrO2 Ceramic Composites

2012 ◽  
Vol 476-478 ◽  
pp. 1031-1035
Author(s):  
Wei Min Liu ◽  
Xing Ai ◽  
Jun Zhao ◽  
Yong Hui Zhou
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Fracture Toughness ◽  
Flexural Strength ◽  
Relative Density ◽  
Sintering Temperature ◽  
Ceramic Composites ◽  
X Ray Diffraction ◽  
X Ray ◽  
Scanning Electron

Al2O3-TiC-ZrO2ceramic composites (ATZ) were fabricated by hot-pressed sintering. The phases and microstructure of the composites were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The relative density and mechanical properties (flexural strength, fracture toughness and Vicker’s hardness) of the composites were tested. The results show that the microstructure of the composites was the gray core-white rim. With the increase of sintering temperature, the relative density and mechanical properties of the composites increased first and then decreased. The composite sintered at 1705°C has the highest synthetical properties, and its relative density, flexural strength, fracture toughness and Vickers hardness are 98.3%,970MPa,6.0 MPa•m1/2and 20.5GPa, respectively.

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.

Mechanical Behavior of the Cr3C2 Compound at High Pressure and High Temperature

2015 ◽  
Vol 1120-1121 ◽  
pp. 1187-1193 ◽  
Author(s):  
Bin Li Jiang ◽  
Zi Li Kou ◽  
De Jiang Ma ◽  
Yong Kun Wang ◽  
Chun Xia Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
High Pressure ◽  
Relative Density ◽  
X Ray Diffraction ◽  
Density Measurements ◽  
X Ray ◽  
Hardness Tests ◽  
Novel Method ◽  
Heat Preservation

In the present study, we present a novel method to sinter Cr3C2 powders under high pressure without any addittives. The sintering Cr3C2 samples were charaterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), relative density measurements, Vicker’s hardness tests and Fracture toughness tests. The reasults show that Cr3C2 powders could be sintered to be bulk under the conditions of 3-5 GPa, 800-1200 °C and the heat preservation for 15 min. Moreover, the sintering body of Cr3C2 compound with the relative density of 99.84% by simultaneously tuning the pressure-temperature conditions exhibited excellent mechanical properties: a Vickers hardness of 20.3 GPa and a fracture toughness of ~8.9 MPam1/2. These properties were much higher than that by using the previous methods. The temperature condition obtained good mechanical properties in the experiment was about 1/3 lower than that using any other methods owing to the high pressure.

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