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

607

3

austenitic stainless steel with average grain size of 35 µm and microhardness of nearly 150HV. Equiaxed grains can be observed in solution annealed sample. Scanning electron micrographs showed banded structured after cold working of samples and band density increased with increase in cold work, which can be seen in Fig. 3.

Fig. 1. Creep specimen design (all dimensions are in mm.)

Fig. 2. Optical micrograph of solution annealed sample

Microhardness of cold worked samples increased with increase in amount of cold work. From initial hardness of 150HV, the hardness increased up to 365HV in CW4 sample. Table 2 showed microhardness of all cold worked samples. It can be observed from hardness results that as the amount of cold working increases, the material undergone through increased work hardening. The increase in hardness is not linear with percentage of cold work. Initially, microhardness increased approximately 80% in CW1 with respect to CW0 and after that successive increase in hardness of 32, 17, and 14% was observed for CW2, CW3, and CW4, respectively.

Table 2. Microhardness of cold worked samples. Sl. No. % Cold work Hardness 1 0 150 2 10 269 3 20 317 4 30 342 5 40 364

Kesternich and Meertens (1986) reported that, uniform dislocation network can be found up to 10% cold work with average dislocation density of 15 x 10 14 m -2 . Higher amount of cold work led to inhomogeneous distribution of dislocation network and resulted in elongated dislocation cells, and formation of deformation bands. Primary