Combined Microwave and Laser Heating for Glazing of 8Y–ZrO2 and 8Y–ZrO2/ZrSiO4–Composites. Issue 2 (4th October 2017)

• Record Type: Journal Article
• Authors: Lehmann, Sebastian; Böckler, Jens; Willert‐Porada, Monika; Rosin, Andreas; Richter, Christian
• Is Part Of: Advanced engineering materials. Volume 20:Issue 2(2018)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2017-10-04
• Subjects: LAMPP -- hot corrosion -- TBC -- zirconia; Materials -- Periodicals; 620.11
• DOI: 10.1002/adem.201700615
• Languages: English
• ISSNs: 1438-1656

Abstract

Abstract : Sintered porous yttria‐stabilized zirconia and zirconia composite ceramics with zirconium silicate are surface glazed by Laser‐Assisted Microwave Plasma Processing (LAMPP). Suitable process parameters for surface glazing are determined for those ceramics. The plasma process is monitored by means of pyrometry and optical emission spectroscopy. In order to prove the quality of the surface glazing and to characterize hot corrosion resistance, tests with molten vanadium pentoxide are performed. After 4 h of exposure, the penetration depth of the molten salt is investigated as a function of ceramic composition and pre‐treatment by glazing. Upon hot corrosion testing of glazed and non‐glazed ceramics, the molten vanadium pentoxide reacts selectively with yttrium oxide, forming yttrium vanadate, and causes crack formation in the zirconia ceramics due to transition to monoclinic zirconia. The results for LAMPP‐glazed ceramics show, that a surficial melting phase is achieved because process temperatures exceed 3000 °C. Hence, a dense, crack‐free and hardness‐enhanced surface layer achieves a better resistance to hot corrosion as compared to non‐glazed ceramics. Due to LAMPP‐glazing, the vanadium ingress is reduced from 33 to 7 μm for yttria‐stabilized zirconia and from 104 to 17 μm for zirconia composite ceramic. Reactions and microstructural changes taking place upon LAMP‐Processing are discussed. Abstract : Suitable process parameters for surface glazing by Laser‐Assisted Microwave Plasma Processing of sintered porous zirconia‐based ceramics are determined. The plasma process is monitored by means of pyrometry and optical emission spectroscopy. Microstructural investigation and phase analysis is performed before and after hot corrosion test with molten vanadium pentoxide. The dense, crack‐free surface layer provides a better resistance to hot corrosion.