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Evaluation of CVD ‐Deposited SiO 2 as a Sintering Aid for Cubic Boron Nitride Consolidated with Alumina by Spark Plasma Sintering
Author(s) -
Zhang Jianfeng,
Tu Rong,
Goto Takashi
Publication year - 2012
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2012.05269.x
Subject(s) - spark plasma sintering , materials science , sintering , boron nitride , tetraethyl orthosilicate , fracture toughness , chemical vapor deposition , nitride , chemical engineering , melilite , layer (electronics) , metallurgy , composite material , nanotechnology , engineering , spinel
A SiO 2 nanolayer, 1.0–2.8 mass% in content, was coated on cubic boron nitride (c BN ) powder by rotary chemical vapor deposition ( RCVD ). The morphology of the SiO 2 nanolayer changed from isolated islands to a continuous layer with increasing supply rate of the precursor, tetraethyl orthosilicate. The effect of the SiO 2 coating on the sinterability and mechanical properties of c BN for machine‐tool applications was evaluated. The SiO 2 ‐coated c BN (c BN / SiO 2 ) powder was mixed with Al 2 O 3 and consolidated by spark plasma sintering ( SPS ) at 1473–1873 K. The phase transformation temperature of c BN to hexagonal BN (h BN ) in Al 2 O 3 –c BN / SiO 2 was 1773 K, 100 K higher than that in Al 2 O 3 –c BN composites. The highest density of the Al 2 O 3 –c BN / SiO 2 composites was 99.5% at 30 vol% c BN / SiO 2 content, at which the microhardness and fracture toughness were 28 GPa and 4.1 MPa·m 1/2 , respectively. This indicates that RCVD ‐deposited SiO 2 is a promising sintering aid for c BN and Al 2 O 3 –c BN / SiO 2 sintered bodies produced by SPS may be applicable as cutting tools.