Fig. 20. Median fatigue life to crack PF-2341066 in a turbo manifold with and without thermal barrier.Figure optionsDownload full-size imageDownload high-quality image (651 K)Download as PowerPoint slide
In the present work, seven different TBCs were applied onto a SiMo51 substrate and tested for their thermal cycling resistance, thermal conductivity, porosity, and hardness. Since the aim was to apply the coating on the inside of a diesel engine exhaust manifold, exposing the coatings to hot, corrosive exhaust gas, the influence of diesel exhaust gas on porosity and hardness was examined. The test coatings included five plasma-sprayed coatings (mullite, forsterite, La2Zr2O7, 8YSZ, and nano-8YSZ) and two sol-gel composite coatings, one sprayed, and one dipped. Below, the results from these tests are linked to a discussion of the requirements of a TBC for this specific application and to the expected effect from internally coating an exhaust manifold.
From this work, histone proteins can be concluded that zirconia coatings show the best performance through their combination of high coefficient of thermal expansion, low thermal conductivity, and high spallation resistance. The literature indicates especially good performance of nanostructured 8YSZ, with a coefficient of 11 × 10− 6 K− 1 (Table 2). This can be compared with mullite, which has a coefficient of only 5.3 × 10− 6 K− 1.