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Materials 2017, 10(5), 461; doi:10.3390/ma10050461

Effects of HfB2 and HfN Additions on the Microstructures and Mechanical Properties of TiB2-Based Ceramic Tool Materials

1
School of Mechanical Engineering, Taiyuan University of Technology, Taiyuan 030024, China
2
Shanxi Key Laboratory of Precision Machining, The Shanxi Science and Technology Department, Taiyuan University of Technology, Taiyuan 030024, China
*
Author to whom correspondence should be addressed.
Academic Editor: Dinesh Agrawal
Received: 23 March 2017 / Revised: 21 April 2017 / Accepted: 25 April 2017 / Published: 27 April 2017
(This article belongs to the Section Advanced Composites)
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Abstract

The effects of HfB2 and HfN additions on the microstructures and mechanical properties of TiB2-based ceramic tool materials were investigated. The results showed that the HfB2 additive not only can inhibit the TiB2 grain growth but can also change the morphology of some TiB2 grains from bigger polygons to smaller polygons or longer ovals that are advantageous for forming a relatively fine microstructure, and that the HfN additive had a tendency toward agglomeration. The improvement of flexural strength and Vickers hardness of the TiB2-HfB2 ceramics was due to the relatively fine microstructure; the decrease of fracture toughness was ascribed to the formation of a weaker grain boundary strength due to the brittle rim phase and the poor wettability between HfB2 and Ni. The decrease of the flexural strength and Vickers hardness of the TiB2-HfN ceramics was due to the increase of defects such as TiB2 coarse grains and HfN agglomeration; the enhancement of fracture toughness was mainly attributed to the decrease of the pore number and the increase of the rim phase and TiB2 coarse grains. The toughening mechanisms of TiB2-HfB2 ceramics mainly included crack bridging and transgranular fracture, while the toughening mechanisms of TiB2-HfN ceramics mainly included crack deflection, crack bridging, transgranular fracture, and the core-rim structure. View Full-Text
Keywords: TiB2-HfB2 ceramics; TiB2-HfN ceramics; hot-pressed sintering; microstructure; mechanical properties TiB2-HfB2 ceramics; TiB2-HfN ceramics; hot-pressed sintering; microstructure; mechanical properties
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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An, J.; Song, J.; Liang, G.; Gao, J.; Xie, J.; Cao, L.; Wang, S.; Lv, M. Effects of HfB2 and HfN Additions on the Microstructures and Mechanical Properties of TiB2-Based Ceramic Tool Materials. Materials 2017, 10, 461.

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