Machinability of Silicon Nitride/Boron Nitride Nanocomposites

Abstract

The machinability and deformation mechanism of Si3N4/BN nanocomposites were investigated in the present work. The fracture strength of Si3N4/BN microcomposites remarkably decreased with increased hexagonal graphitic boron nitride (h‐BN) content, although machinability was somewhat improved. However, the nanocomposites fabricated using the chemical method simultaneously had high fracture strength and good machinability. Hertzian contact tests were performed to clarify the deformation behavior by mechanical shock. As a result of this test, the damage of the monolithic Si3N4 and Si3N4/BN microcomposites indicated a classical Hertzian cone fracture and many large cracks, whereas the damage observed in the nanocomposites appeared to be quasi‐plastic deformation.

Preparation and mechanical properties of machinable alumina/mica composites

“…The bending strength was 400-450 MPa, which were the same level as that of the conventional monolithic alumina ceramics while the fracture toughness was 3.7-3.9 MPa·m 0.5 , which were little higher than that of the conventional monolithic alumina ceramics. The Vickers hardness was [11][12][13][14] GPa, which was the same level as that of zirconia ceramics. 9.…”

Fabrication of Boron Nitride Dispersed Nanocomposites by Chemical Processing and Their Mechanical Properties

“…Thus, it is concluded that the observed high strength of SiCBN nanocomposites is attributable mainly to the reduction of the critical flaw size by the nano-sized h-BN dispersion. The mechanical properties of h-BN dispersed nanocomposites [23][24][25][32][33][34] are summarized in Table. 1. It is found that all the produced h-BN dispersed nanocomposites have the unique mechanical property of high strength though low Young's modulus.…”

Machinability and Contact Damage of Al2O3/BN Composites Fabricated through Chemical Processing

“…For fabrication of Al 2 O 3 /BN nanocomposites, the process presented in previous paper 12) was adopted. The starting powders for the nanocomposites were the commercially available aAl 2 O 3 powder (AKP53, Sumitomo Chemicals, Tokyo) and boric acid (Reagent grade, Wako Pure Chemi Fig.…”

“…8)11) However, by the addition of microsized hBN particles as a second phase, it has been reported that fracture strength decrease remark ably with an increase in hBN content due to the aggregation of BN particles caused by conventionally mixing commer cially powders, even though its machinability was somewhat improved. 10) Also, large grain size hBN particle maybe in itiate fracture, because Young's modulus of hBN is lower than 1/6 of that of monolithic Al 2 O 3 . Therefore, for hBN dispersed ceramic composites, the nanocomposite struc ture, which is the homogeneous dispersion of nanosized h BN particles into Al 2 O 3 matrix, is probably eective to en hance the fracture strength of machinable Al 2 O 3 /BN compo sites.…”