Study on the Multi-Scale Nanocomposite Ceramic Tool Material

Abstract

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.

Influence of uni and bi-modal SiC composition on mechanical properties and microstructure of reaction-bonded SiC ceramics

“…4) seen in the SC-E sample may lead to high fracture energy dissipation. 24) This fractured result can contribute to the improvement of the mechanical properties, resulting in high fracture toughness.…”

Effect of special microstructure on the mechanical properties of nanocomposite

“…The multi-scale nanocomposite ceramic tool material ASs was successfully fabricated, its comprehensive mechanical properties are much higher than that of other composites fabricated with single nano-scale SiC or with single micro-scale SiC [10]. Besides the contribution of the ordinary transgranular fracture mode and the refining of matrix grain to the improvement of the mechanical properties, the contribution of special microstructure observed in ASs should not be ignored.…”

“…The well dispersed powder mixture was hot-pressed in nitrogen atmosphere in a graphite mold at 1700 • C under a pressure of 30 MPa to obtain circular disks of approximately 41 mm in diameter and 4.7 mm in thickness. Other detailed procedures for fabricating and testing method were described in literature [10].…”

“…Almost all the reported Al 2 O 3 /SiC nanocomposites were fabricated with single micro-scale Al 2 O 3 as matrix with an incorporation of single nano-scale SiC, and the results showed the significant improvement in the flexural strength while the modest increase in fracture toughness [3,5]. Considering the good strengthening effect of nano-scale particles and the good toughening effect of economical micro-scale particles, also according to the report [9] that the multi-scale particles with random distribution were easier to obtain the high density than single-scale ones, the multi-scale nanocomposite concept was proposed in order to get higher comprehensive mechanical properties [10]. Primary work for the multi-scale Al 2 O 3 /SiC /SiC n nanocomposite with the incorporation of both micro-scale SiC (marked as SiC ) and nano-scale SiC (marked as SiC n ) has shown the expected results, in which the average flexural strength is 705 MPa and the fracture toughness is 8.45 MPa m 1/2 .…”

“…Primary work for the multi-scale Al 2 O 3 /SiC /SiC n nanocomposite with the incorporation of both micro-scale SiC (marked as SiC ) and nano-scale SiC (marked as SiC n ) has shown the expected results, in which the average flexural strength is 705 MPa and the fracture toughness is 8.45 MPa m 1/2 . The strengthening and toughening mechanisms were primarily discussed in the previous paper [10], the present work attempts to investigate the microstructure deeply with TEM and high-resolution transmission electron microscopy (HRTEM) morphology in order to further clarify the toughening mechanisms of multi-scale ceramic nanocomposite.…”