Properties of nitrogen-implanted alloys and comparison materials

Autor: L. Riester, J.M. Williams, R. Pandey, Alan W. Eberhardt
Rok vydání: 1997
Předmět:
Zdroj: Surface and Coatings Technology. 88:132-138
ISSN: 0257-8972
DOI: 10.1016/s0257-8972(96)02912-x
Popis: The nanoindentation hardness technique and the atomic force microscopy technique have been combined in a study of surface and near-surface properties of nitrogen ion-implanted alloys versus ion fluence. The two alloys studied were Ti-6Al-4V and a CoCrMo alloy. Properties results have been compared with those of non-ion-implanted reference materials, such as electroplated hard chrome, rutile, and amorphous TiO2. Large areas of both alloys were polished to finish levels of approximately 1 nm, but for the CoCrMo, the finish level, by profilometer, over long traces is limited to about 30 nm. This results from the very different hardnesses of the carbide and matrix phases of the CoCrMo. In either case, nanoindentations of only 50 nm in depth still penetrate to about 50 times the local roughness values. The alloys were ion implanted to the same respective treatment depths (150 nm) by use of an energy grade suitable for each alloy. By 6 × 1017 cm−2, the hardness of the Ti-alloy had increased from a value of 4 to 12 GPa. A rutile crystal was amorphized by ion bombardment, so that a hardness value for amorphous TiO2 could be obtained. The results indicate that after only a small dose, the Ti alloy is harder than its own passive oxide. Ion implantation first softens and then rehardens the carbide phase of the CoCrMo. The matrix of that alloy is not quite as hardenable as the Ti-6Al-4V alloy. These results are relevant to orthopedics applications, tribological mechanisms, ion implantation process design, and substitute coatings for electroplated hard chrome.
Databáze: OpenAIRE
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