EFFECT OF TENSILE STRESS ON STRESS CORROSION CRACKING OF MATERIALS UNS C70600 IN AMMONIA AND SULFIDE ENVIRONMENTS
Heat exchangers are static equipment for heating or cooling a fluid in the form of combustion gas, steam or water to form a gas, vapor, or various types of liquid. The main function of the tube in heat exchanger is to transfer heat from the shell into fluid inside the tube and vice versa. Corrosion...
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| Format: | Final Project |
| Language: | Indonesia |
| Online Access: | https://digilib.itb.ac.id/gdl/view/49547 |
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| Institution: | Institut Teknologi Bandung |
| Language: | Indonesia |
| Summary: | Heat exchangers are static equipment for heating or cooling a fluid in the form of combustion gas, steam or water to form a gas, vapor, or various types of liquid. The main function of the tube in heat exchanger is to transfer heat from the shell into fluid inside the tube and vice versa. Corrosion resistance that must be possessed by tube material are resistance to general corrosion, stress corrosion craking (SCC), selective leaching (dezincification on brass or denickelification on cupronickel), and the influence of fluid flow (erosion corrosion and fouling).
This reaserch will study the resistance of UNS C70600 material to stress corrosion cracking (SCC) with the immersion and vapor methods using static loading of C-ring samples. The tensile stresses used in the specimens were 75, 100, 115% of the yield strength UNS C70600 material in corrosion media of 10% ammonia, 10% Na2S, and a mixture of ammonia and 10% Na2S. The duration of the test for 15 days was determined based on calculations on ASTM G31 and previous experiments conducted by the author.
The results of visual macroscopic evaluation showed that all specimens undergo general corrosion and there were no cracks on their outer surfaces. The corrosion product of immersion and vapor methods is dominated by copper in the form of Cu (OH), Cu2S, copper ammonium ion complex, which is blue to black. Microstructure evaluation results show that intergranular corrosion take place on immersion specimens and vapor undergo pitting corrosion. Tensile stress was not affect the mechanism corrosion of UNS C70600 material based on the results of weight loss percentage specimens of liquid sulfide media, ammonia vapor media, and mixed ammonia media with sulfide in liquid and vapor which have the same relative value of 5 to 6%. It was concluded that the UNS C70600 material in testing duration 15 days was undergo to a stress corrosion cracking (SCC) incubation stage.
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