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Creep rupture of Nimonic-90 under salt-induced high temperature corrosion
| Content Provider | Semantic Scholar |
|---|---|
| Author | Ghosh, K. S. |
| Copyright Year | 2000 |
| Abstract | Materials used in hot section components of gas and steam turbines , boilers , etc., undergo deterioration and degradation due to simultaneous actions of aggressive salts deposit hot corrosion and mechanical stresses developed at the high operating temperatures. Creep-ruptured properties are reported here at different stres s levels at 650, 700 and 750°C on Nimonic-90 specimens in air and coated with ternary salt mixture of Na2S04-NaVOrNaCI (in 50, 30 and 30 mole %). To assess the extent of hot corrosion, coupons of Nimonic-90 uniformly coated with the ternary salt mixture are exposed into a furnace for 170-180 h at 650, 700 and 750°C. The various corrosion products have been identified by XRD technique. The probable chemical reactions and hot corrosion mechanisms are also discussed. Materials used in hot section components of gas and steam turbines, boilers, refinery furnaces and 'heat exchangers are subjected to aggressive environments and mechanical stresses developed at the high operating temperature 1-4. The aggressive environ ments cause chemical attack and consequently structural alteration resulting degradation of mechanical properties. Degradation effects essentially are due to : (i) reduction of load bearing cross-section (ii) loss of alloying elements, and (iii) stress associated to the corrosion products 5 ,6. The chemical attack is caused by the salts, e.g., sodium sulphate and a series of vanadium compounds arising from the combustion products. Further, if the gas turbine is operated in marine atmosphere, NaCl particles are ingested into the turbines predominantly as an aerosol of sea salt together with the intake air. As a result, the salt deposits comprise of a complex mixture of sodium sulphate-vanadium compounds-sodium chloride 7 - 9 . Therefore, the high temperature materials being utilised should be evaluated for performance considering high temperature corrosion and their influence on mechanical properties in stead of high temperature corrosion alone or mechanical properties separately. Creep-corrosion interaction studies are reported in environments such as sodium sulphate, mixtures of sodium sulphate-sodium vanadate, sodium sulphate-sodium chloride 1o 12 , and sodium |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://nopr.niscair.res.in/bitstream/123456789/24385/1/IJEMS%207(2)%2069-76.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
