PSI - Issue 14

Hari Krishan Yadav et al. / Procedia Structural Integrity 14 (2019) 605–611 Hari krishan Yadav/ Structural Integrity Procedia 00 (2018) 000–000

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titanium carbides dissolved during solution treatment and re-precipitation took place during creep exposure, which provides better mechanical strength to the material, Vijayanand et al. (2013).

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Fig. 3. Scanning electron micrographs of (a) CW1; (b) CW2; (c) CW3; (d) CW4 steel

3.2 Creep rupture properties Creep test results are shown in Table 3. Cold worked samples shows better creep strength as compared to that of solution annealed sample. However, CW2 sample showed highest creep strength among all. Fig. 4 shows strain rate vs rupture time of all samples. CW2 showed the minimum creep rate of 6.5E-06 h -1 . Creep rupture strength significantly improved after cold working. However, this improvement was not found to be linearly dependent on percentage of cold work. Rupture strength increased up to CW2 and then decreased. CW4 is exhibiting lowest creep life among cold worked samples. Secondary creep region was more pronounced in cold worked samples as against almost negligible in the case of CW0. Onset of tertiary stage was also delayed and it varied with different samples. Rupture elongation was more in CW4, which represent drastic recovery of highly strained microstructure and recovery and recrystallization phenomenon was more pronounced in CW4. This led to formation of softer grains and material deformed in much easily and led to decrease in creep resistance of material, Kesternich and Meertens (1986). Fig. 5 showed creep rupture life at various cold work conditions.