Graded coatings by gradient temperature densification

• Published in: Journal of materials research Vol. 13; no. 5; pp. 1255 - 1259
• Main Authors: Hur, Sung Kang, Yoo, Sang H., Groza, Joanna R., Doh, Jung Man, Yamazaki, Kazuo, Shoda, Kazuo
• Format: Journal Article
• Language: English
• Published: New York, USA Cambridge University Press 01.05.1998
• ISSN: 0884-2914; 2044-5326
• DOI: 10.1557/JMR.1998.0179

Functionally gradient materials (FGM) were prepared using layers of ZrO2 –3 mol% Y2O3 ceramic and NiCrAlY powders. A fine-grained zirconia powder was chosen to lower the ceramic sintering temperature and achieve simultaneous metal and ceramic densification. Consolidation of FGM's was achieved by a short time field-assisted sintering technique. Sintering was performed either at a constant temperature or in a temperature gradient by using punches made of different materials (i.e., one graphite and one tungsten). A temperature gradient of at least 100 °C was required with a low value of 1200 °C at the metal end and exceeding 1300 °C at the ceramic end. Increasing the number of intermediate layers alleviates some of the cracks formed during sintering due to different coefficients of thermal expansion.