Thermal barrier coatings (TBCs) thermally insulate the substrate from high temperature exposure. This work attempted to simulate real engine thermal cyclic conditions by designing a test method to evaluate the thermal cyclic fatigue (TCF) performance of different coatings applied inside exhaust manifold of a diesel engine. The coatings investigated in this work comprised of two plasmas-sprayed TBCs (conventional 8YSZ and nanostructured 8YSZ) and one bond coat (NiCoCrAlY). Additionally, these coatings were exposed to isothermal testing and their oxidation behavior was evaluated. All the coatings along with only substrate were exposed to temperature around 525°C for 150 cycles in thermal cyclic testing carried out on Scania’s heavy-duty diesel engine. For isothermal testing, all coatings along with only substrate material were exposed to 650°C and 750°C for 168 hours respectively. Microstructural analysis by SEM/EDS was carried out to compare the microstructural evolution of the tested coatings with the as sprayed TBCs. In the case of thermal cyclic test, all coatings showed no failure and no TGO growth up to 150 cycles. In the EDS analysis for isothermally tested coatings, oxidation of the substrate at bond coat- substrate interface instead of TGO growth was observed. Bond coat showed lowest oxide layer thickness at 650°C and 750°C followed by conventional YSZ and then nanostructured YSZ. But, conventional YSZ showed microcracks in top coat near top coat- bond coat interface after isothermal testing. Thermal cyclic and isothermal exposure test results showed that bond coated substrate and nanostructured YSZ have the potential to be implemented inside the real manifold.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:hv-11680 |
| Date | January 2017 |
| Creators | Bhoje, Sourabh |
| Publisher | Högskolan Väst, Forskningsmiljön produktionsteknik(PTW) |
| Source Sets | DiVA Archive at Upsalla University |
| Language | Swedish |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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