Nanocomposite Ceramic Tool Research Articles

Microstructure and Mechanical Properties of Multi-Scale Titanium Diboride Matrix Nanocomposite Ceramic Tool Materials

Under the liquid-phase hot-pressing technique, the multi-scale titanium diboride matrix nanocomposite ceramic tool materials were fabricated by adding both micro-scale and nano-scale TiN particles into TiB2 with Ni and Mo as sintering aids. The effect of content of nano-scale TiN and sintering temperature on the microstructure and mechanical properties was studied. The result showed that flexural strength and fracture toughness of the composites increased first, and then decreased with an increase of the content of nano-scale TiN, while the Vickers hardness decreased with an increase of the content of nano-scale TiN. The optimal mechanical properties were flexural strength 742 MPa, fracture toughness 6.5 MPa•m1/2 and Vickers hardness 17GPa respectively. The intergranular and transgranular fracture mode were observed in the composites. The metal phase can cause ductility toughening and crack bridging, while crack deflection and transgranular fracture mode could be brought by micro-scale TiN and nano-scale TiN respectively.

Simulation of the Effect of Initial Grain Size of Matrix on Microstructure Evolution in Nano-Composite Ceramic Tool Material

A new Monte Carlo Potts′ model for the sintering process of two-phase nano-composite ceramic materials with various grain size of initial matrix is set up. The grain growth process is successfully investigated assuming the green body is completely dense. The effect of the initial matrix grain size on microstructure evolution is observed and discussed quantitatively.

Cutting performance and failure mechanisms of an Al2O3/WC/TiC micro- nano-composite ceramic tool

Abstract An Al2O3-based composite ceramic tool material reinforced with WC microparticles and TiC nanoparticles was fabricated by using hot-pressing technique. The cutting performance, failure modes and mechanisms of the Al2O3/WC/TiC ceramic tool were investigated via continuous and intermittent turning of hardened AISI 1045 steel in comparison with those of an Al2O3/(W, Ti)C ceramic tool SG-4 and a cemented carbide tool YS8. Worn and fractured surfaces of the cutting tools were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results of continuous turning revealed that tool lifetime of the Al2O3/WC/TiC ceramic tool was higher than that of the SG-4 and YS8 tools at all the tested cutting speeds. As for the intermittent turning, tool life of the Al2O3/WC/TiC ceramic tool was equivalent to that of YS8, but shorter than that of the SG-4 at lower cutting speed (110 m/min). However, tool life of the Al2O3/WC/TiC ceramic tool increased when the cutting speed increased to 170 m/min, becoming much longer than that of the SG-4 and YS8 tools. The longer tool life of the Al2O3/WC/TiC composite ceramic tool was attributed to its synergistic strengthening/toughening mechanisms induced by the WC microparticles and TiC nanoparticles.

Processing and characterization of an Al 2O 3/WC/TiC micro- nano-composite ceramic tool material

An Al 2O 3-based composite ceramic tool material reinforced with WC microparticles and TiC nano-particles was fabricated by using hot-pressing technique with MgO and NiO as sintering aids. The experimental results showed that optimal mechanical properties were achieved for the composite with the addition of 24 vol.% TiC nano-particles and 16 vol.% WC microparticles, with the flexural strength, fracture toughness and Vicker's hardness being 842 MPa, 6.82 MPa m 1/2 and 22.19 GPa, respectively. The microstructure and phase composition of the composites were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The fracture surface of the Al 2O 3/16 vol.%WC/24 vol.%TiC micro- nano-composite was characterized by a mix of intergranular and transgranular fracture as a result of the presence of both intergranular and intragranular secondary phase particles. It is believed that inhibition of matrix grain growth by intergranular secondary phase particles, sub-grain boundaries and dislocations pinning inside Al 2O 3 grains induced by intragranular TiC nano-particles contribute to the strengthening of the composite. Meanwhile, the dislocations and microcracks inside the matrix grains can also increase the flaw-tolerance leading to high toughness of the composite. Additionally, some extrinsic processes including crack deflection, crack bridging and crack branching caused by the microstructural discontinuities and local stress state can absorb a great amount of fracture energy, which are beneficial for the toughening of the composite. However, future research will need to quantitatively understand the synergistic effect of TiC nano-particles and WC microparticles on strengthening and toughening mechanisms.

Development of Self-Toughening Silicon Nitride Matrix Nanocomposite Ceramic Tools and Cutting Performance

A series of self-toughening silicon nitride matrix nanocomposite ceramic tool materials are fabricated by hot-press technology at different sintering processes. And their microstructure has been observed and analyzed by a scanning electron microscope (SEM). Finally, the tests of mechanical properties and the cutting performance of the new ceramics are presented. The research results showed that the nanocomposite ceramic tool materials GGW20T5 and GGW20TC25 have better mechanical properties and possess a stronger wear resistance in cutting 40Cr alloy steel.

New Thought for Designing the Multi-Phase and Multi-Scale Nanocomposite Ceramic Tool Materials

The new thought for designing the multi-phase and multi-scale nanocomposites was proposed to improve the comprehensive mechanical properties. Multi-phase and multi-scale particles are added to the matrix, and one of the additives is nano-scale particle, thus the comprehensive mechanical properties can be improved by the synergic effects of micro-scale toughening, nano-scale strengthening and mutual benefit between multi-phases. The ideal microstructure of multi-phase and multi-scale nanocomposites was designed. With this microstructure, the trans/intergranular fracture modes can be formed, which will consume more fracture energy during the crack propagation, therefore, both the flexural strength and fracture toughness can be improved. An advanced ceramic tool material has been fabricated based on this new thought.

Study of the mechanical properties, toughening and strengthening mechanisms of Si 3N 4/Si 3N 4w/TiN nanocomposite ceramic tool materials

Si 3N 4/Si 3N 4w/TiN nanocomposites were fabricated by a hot-pressing technology with different sintering processes. The effect of nanoscale TiN and Si 3N 4w on the mechanical properties was investigated. The microstructure and indention cracks were observed by scanning electron microscopy, transmission electron microscopy and energy-dispersive spectrometry investigations. The research results showed that Si 3N 4/Si 3N 4w20/TiN5 nanocomposites containing 5 vol.% of nanoscale TiN and 20 vol.% of nanoscale Si 3N 4w, which were sintered under a pressure of 30 MPa at a temperature of 1650 °C for 40 min, had optimum mechanical properties. The addition of both nanoscale TiN and nanoscale Si 3N 4w contributed to the microstructural evolution and an improvement of the mechanical properties. The toughening and strengthening mechanisms are discussed for Si 3N 4/Si 3N 4w20/TiN5 nanocomposites.

Multi-scale and multi-phase nanocomposite ceramic tools and cutting performance

An advanced ceramic cutting tool material Al_2O_3/TiC/TiN(LTN)is developed by incorporation and dispersion of micro-scale TiC particle and nano-scale TiN particle in alumina matrix.With the optimal dispersing and fabricating technology,this multi-scale and multi-phase nanocomposite ceramic tool material can get both higher flexural strength and fracture toughness than that of Al_2O_3/TiC(LT)ceramic tool material without nano-scale TiN panicle,especially the fracture toughness can reach to 7.8 MPa·m~(0.5).The nano-scale TiN can lead to the grain fining effect and promote the sintering process to get a higher density.The coexisting transgranular and intergranular fracture mode induced by micro-scale TiC and nano-scale TiN,and the homogeneous and densified microstructure can result in a remarkable strengthening and toughening effect.The cutting performance and wear mechanisms of the advanced multi-scale and multi-phase nanocomposite ceramic cutting tool are researched.

Study on the Multi-Phase and Multi-Scale Nanocomposite Ceramic Tool Material

An advanced ceramic cutting tool material Al2O3/TiC/TiN is developed by means of adding micro-scale TiC particle and nano-scale TiN particle dispersion. With an optimal dispersing and fabricating technology, this multi-scale and multi-phase nanocomposite may get both higher flexural strength and fracture toughness, especially the fracture toughness may reach to 7.8 MPa·m1/2. The micro-scale TiC particle will form the framework microstructure with other particle and the particles will inlay each other. That is why the flexural strength of Al2O3/TiC composite is improved. Another phase such as nano-scale TiN may lead to fining the grains further more, and promote the sintering to get higher density. The uniform and densified microstructure is obtained, the coexisting transgranular and intergranular fracture mode induced by micro-scale TiC and nano-scale TiN can result in remarkable strengthening and toughening effect.

Study on the Multi-Scale Nanocomposite Ceramic Tool Material

An advanced ceramic cutting tool material was developed by means of micro-scale SiC particle cooperating with nano-scale SiC particle dispersion. With the optimal dispersing and fabricating technology, this multi-scale nanocomposite may get both higher flexural strength and fracture toughness than that of the single-scale composite. The improved mechanical properties may be mainly attributed to the inter/intragranular microstructure with a lot of micro-scale SiC particles located on the grain boundary and a few nano-scale SiC particles located in the matrix grain. Because of the thermal expansion mismatch between SiC and Al2O3 resulting in the compressive stress on the SiC/Al2O3 interface, the interface bonding strength between Al2O3 and SiC was reinforced, which can compel the crack propagating into the relatively weak matrix when meeting the SiC particle on the boundary; while the alumina grain boundary is not the same strong as the SiC/Al2O3 interface and the Al2O3 grain, therefore the crack propagates sometimes along the Al2O3 grain boundaries and sometimes through the grains, when reaching to the nano-scale SiC particle inside the matrix, the crack was pinned and then deflected to the sub-grainboundaries. These coexisting transgranular and intergranular fracture mode induced by micro-scale and nano-scale SiC and the fining of matrix grain derived from the nano-scale SiC resulted in the remarkable strengthening and toughening effect.