| Project/Area Number |
02650516
|
|---|
| Research Category |
Grant-in-Aid for General Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Research Field |
金属材料(含表面処理・腐食防食)
|
|---|
| Research Institution | Nagoya University |
|---|
Principal Investigator |
KURODA Kotaro. Nagoya University, Faculty of Enginering Department of Materials Science and Engineering, 工学部, 講師 (30161798)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
SAKA Hiroyasu Nagoya University Faculty of Enginering Department of Materials Science and Engi, 工学部, 教授 (90023267)
|
|---|
| Project Period (FY) |
1990 – 1991
|
| Project Status |
Completed (Fiscal Year 1991)
|
| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1991: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1990: ¥1,600,000 (Direct Cost: ¥1,600,000)
|
|---|
| Keywords | Plasma-spraying / Ceramic coatings / Mullite / Forsterite / Alumina-zirconia / Microstructure / Transmission electron microscopy / Analytical electron microscopy / 溶射皮膜 / アルミナ-ジルコニア / 透過電子顕微鏡 / アルミナ-クロミア / ジルコン |
|---|
| Research Abstract |
Plasma-sprayed ceramic coatings exhibit characteristic microstructures formed by rapid solidification. Amorphous and/or metastable phases are frequently retained in the coatings. Thermal stability of such phases is of interest both from metallographic and practical points of view. In this study, microstructural and microchemical characterization has been carrid out on plasma-sprayed oxide coatings by analytical transmission electron microscopy.
The as-sprayed mullite (3Al_2O_3・2SiO_2) coatings consist mostly of Al_2O_3 rich mullite crystal and amorphous phases. SiO_2 is thought to be vaporized during plasma-spraying. In some regions, polycrystalline gamma-Al_2O_3 with a grain size of 0.1 mum is also observed. The as-sprayed forsterite (2MgO・SiO_2) coatings consist of clinoenstetite (MgO・SiO_2) crystal and amorphous phases. The loss of MgO takes place during plasma-spraying. The as-sprayed 70% alumina-zirconia coatings consist of crystalline and amorphous phases, but these two phases shows differrent composition in contrast with mullite of forsterite coatings. The crystalline phase is identified as a gamma-Al_2O_3 having a trace of Zr. Chemical analysis in the electron microscope indicates that the amorphous phase is the eutectic composition.
The crystallization of amorphous phases in mullite and forsterite coatings rapidly takes place at 970 and 875ﾟC, respectively. The amorphous phase in alumina-zirnonia coatings crystallizes at 940ﾟC. Microstructure of the annealed alumina-zirnonia coatings indicates mixture of small particles of zirconia and alumina. Rapid crystallization of amorphous phases in the plasma-sprayed coatings studied here indicates that the coatings will show possible unstability in use at high temperatures.
|
