## Abstract

Here we report for the first time experimental results of the nanohardness and elastic properties (Young's modulus, shear modulus, bulk modulus) of well-characterised complete series of bulk Ti, Zr and Hf carbonitrides, Ti(C_{x}N_{1-x}), Ti(C_{x}N_{1-x})_{0.81}, Zr(C_{x}N_{1-x}) and Hf(C_{x}N_{1-x}), as a function of the carbon/nitrogen ratio measured by continuous nano-indentation test and an ultrasonic technique. A correlation between elastic constants and porosity of TiC and TiN was obtained and used to correct elastic constants for the zero-porosity state. Recently, band structure calculations for transition metal carbonitrides yielded a maximum of the shear modulus of Ti and Hf carbonitrides at a valence electron concentration (VEC) of ≈ 8.4 and ≈ 8.2, respectively. These results were used to explain the hardness maximum of carbonitrides, which was considered as a success of theoretical material design. For the stoichiometric carbonitrides we indeed found - though much weaker than predicted - the maximum at [C]/([C] + [N]) ≈ 0.6-0.8 (VEC ≈ 8.4-8.2) of the shear modulus, but neither the nanohardness nor the microhardness show a corresponding maximu. Thus the conclusion of a correlation of hardness and shear modulus is inapplicable for this type of hard materials.

Original language | English (US) |
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Pages (from-to) | L5-L9 |

Journal | Journal of Alloys and Compounds |

Volume | 309 |

Issue number | 1-2 |

DOIs | |

State | Published - Sep 14 2000 |

## All Science Journal Classification (ASJC) codes

- Mechanics of Materials
- Mechanical Engineering
- Metals and Alloys
- Materials Chemistry

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