✍ Scribed by Ass. Prof. Dr. K. Prasad Rao; Dr. K. S. Raja
No coin nor oath required. For personal study only.
The main aim of the work was to study the effect of applied potentials (both cathodic and anodic) on the environmental cracking behaviour of 17‐4 PH stainless steel material. For this a 1.5 mm thick 17‐4 PH sheet was taken and subjected to 1. solutionising (1050 °C, 45 min, air cooled) and 2. solutionising followed by aging treatments. Aging was carried out at 480 °C for 1 hr, 510 °C for 4 hrs and over aging at 550 °C for 2 hrs and 600 °C for 4 hrs. U‐bend samples were made according to ASTM standard G30‐79 for environmental cracking studies. Samples were tested in 3.5%, NaCl solution (pH = 2.0) under various applied potentials and the failure time at each potential was noted. Fractography was done using scanning electron microscope.
Under the open circuit potentials both the solution treated samples and the over aged samples were found to be highly resistant to environmental cracking while the peak aged samples were found to be inferior. Under highly cathodic potentials, the over aged samples exhibited relatively better resistance than the other samples. At relatively less cathodic potentials, the solution treated samples, too, had better resistance. The peak aged samples failed very quickly by the application of cathodic potentials whether highly cathodic or not. Under the anodic potentials, the solution treated samples exhibited better resistance to cracking. Active path dissolution was found to be operative under anodic potentials while hydrogen absorption under cathodic potentials.
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