| Title |
Thermo-mechanical Degradation of NiCr Thin Film Subjected to Thermal Cycling |
| Authors |
(Eui Jong Lee); (Tai Min Noh); (Min Seok Jeon); (Hyun Gyoo Shin); (Hee Soo Lee) |
| DOI |
https://doi.org/10.3365/KJMM.2013.51.2.131 |
| ISSN |
1738-8228(ISSN), 2288-8241(eISSN) |
| Keywords |
NiCr film; thermal cycling; accelerated test; degradation; failure mechanism |
| Abstract |
The thermo-mechanical degradation of NiCr films during thermal cycling was investigated in terms of microstructural and chemical changes to the surface. Thermal cycling was performed between room temperature and 200℃ in thermally evaporated NiCr films on an Mn-Ni-Co-O substrate. Isothermal exposures were also performed as a control experiment. The sheet resistance of the NiCr films increased linearly (from 35 to 52 Ω/sq.) with a temperature difference of the thermal cycling, whereas the films subjected to isothermal aging increased only slightly, from 35 to 38 Ω/sq. After 300 thermal cycles at ΔT=175℃, cracks formed and proliferated on the coating surface, and local delamination occurred at the interfaces. XPS results showed that the intensity of a metallic peak at 574.0 eV decreased and that of the Cr oxide peak at ~577 eV increased with an increase of the thermal cycles. Consequently, the degradation of the NiCr films by accelerated thermal cycling stress was attributed to a proliferation of lateral surface cracks from thermally induced tensile stress compounded by surface oxidation, causing an increase in sheet resistance. |