The 400°C limitation to the most common nanoindenter material, diamond, is not due to diamond changing to graphite in air, which can happen above 750°C, but to the reaction of the nanoindenter with the sample, causing a change in the geometry. The nanoindentation methodology is very sensitive to a change in nanoindenter geometry, thus the typical solution for measurements above 400°C is to use a cBN nanoindenter. However, the cBN indenter that is commercially used at temperatures above 400°C is too soft for measuring hard coatings such as machine tool coatings. There is limited published research on improving nanoindentation measurements in this way. Thus, the objective of this thesis is to address whether a coated diamond could be used for nanoindentation between 400-750°C.
Due to the results of early experiments PVD titanium is the focus of this thesis as it will adhere to diamond by forming a carbide interlayer, TiC. A methodology to determine the best coating based on resistance to oxidation and robustness of the coating at temperature was used, allowing the exploration of several different titanium based alloys and coating thickness. The methodology used is as follows:
1. PVD coatings of titanium and titanium based alloys TiAl, TiN, and TiAlN were oxidized at 500, 575, and 650°C. Measurements by SEM and EDS were taken after the oxidation at each temperature. Of the coatings tested, the pure titanium coating was determined to be the best coating.
2. The coating thickness of 0.25, 0.50, and 1.0 um were evaluated with the same static oxidation test applied to the different alloys. It was determined that 0.50 um was the best thickness. A duplicate 0.50 um thick sample had a cross-section machined by FIB, and was examined by STEM, HAADF and EELS. The results confirmed that TiC was being formed at the expected rate.
3. To determine whether a coated nanoindenter could be used for measurements, a nanoindenter was first calibrated, coated by PVD with 0.50 um thick titanium, and calibrated again. The results confirmed that a coated nanoindenter could be used for performing nanoindentation measurements.
4. To determine whether the titanium PVD coating would adhere to the diamond at temperature, a coated nanoindenter was used to measure fused silicon at 450°C. After each measurement, the nanoindenter was examined by SEM and EDS. The results confirmed that the titanium coating adhered to the diamond.
This thesis demonstrates that a titanium PVD coating can protect a diamond nanoindenter during measurements between 400-750°C. The primary contributions are that coated diamond nanoindenters can be used for nanoindentation measurements, and that titanium PVD coated nanoindenters can be used for nanoindentation measurements between 400-750°C. Additional contributions include the testing of adhesion of titanium PVD coating to diamond between 400-750°C, and a methodology of evaluating coatings. / Thesis / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/27824 |
| Date | January 2022 |
| Creators | Weaver, Andrew S. |
| Contributors | Veldhuis, Stephen, Mechanical and Manufacturing Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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