Corrosion behaviour of gas-pressure sintered silicon nitride with the additions of yttria and alumina is investigated in boiling sulphuric acid. In the corrosion tests of 6 N boiling sulphuric acid, the strength of the specimens gradually decreases with time exposed in the corrosive solutions, while a rapid decrease in strength seems to occur in the initial stage of corrosion. A gradual decrease in strength with time is analysed in terms of thickness of the corroded layer, which is caused by the selective corrosion of grain boundaries. The strength is strongly dependent on the thickness of the corroded layer beyond 100 pm, while the strength is approximately held constant when the thickness of the corroded layer is less than 100 μm. From the strength dependence on the corroded layer thickness, it is suggested that a penny-shape crack having a diameter corresponding to the dimension of the corrosion layer governs the fracture strength.
|Number of pages||10|
|Journal||Key Engineering Materials|
|Publication status||Published - 1996 Jan 1|
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Mechanics of Materials
- Mechanical Engineering