Ultramicrohardness cross-profiling of CVD diamond/steel brazed junctions
| Autor: | M.J Fonseca, António J. S. Fernandes, Florinda M. Costa, Rui F. Silva, M.H. Nazaré |
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| Rok vydání: | 1999 |
| Předmět: |
Materials science
Filler metal Mechanical Engineering Metallurgy Diamond General Chemistry Chemical vapor deposition engineering.material Thermal expansion Electronic Optical and Magnetic Materials Flexural strength Indentation Materials Chemistry engineering Brazing Electrical and Electronic Engineering Layer (electronics) |
| Zdroj: | Diamond and Related Materials. 8:855-858 |
| ISSN: | 0925-9635 |
| DOI: | 10.1016/s0925-9635(98)00320-3 |
| Popis: | Thick microwave plasma chemical vapour deposition (MPCVD) diamond films (240, 480, 1000 μm) were grown, laser cut and vacuum brazed to steel bars with an Ag/Cu/Ti (100 μm) reactive filler metal. Displacement sensing indentation experiments using a dynamic ultramicrohardness tester on the brazing layer were performed on different samples. A calibration curve for the residual depth values was made by linear regression to diagonal measurements on Vickers impressions. Corrected depth values were then used to evaluate the hardness. The thicker the films were, the higher the hardness was found to be. Hardness changes from 1.35 to 1.72 GPa, respectively, for the thinnest and the thicker film joints, getting an increment of ca 35%. These data indicate a hardening effect during the cooling stage caused by thermal expansion coefficients mismatch. An increment of ca 25% on the flexural stresses imposed by the film/substrate curvature was theoretically evaluated. The same trend variation with film thickness was found for both the hardness values and the brazing strength from previous work. Brazing layer hardness evaluation can be regarded as a non-destructive indirect way to assess the mechanical resistance of the diamond/steel joints. |
| Databáze: | OpenAIRE |
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