PSI - Issue 14

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S Usha Rani et al. / Procedia Structural Integrity 14 (2019) 142–149 Author name / Structural Integrity Procedia 00 (2018) 000–000

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a

b

c

e

d

f

g

h

i

Fig. 5: Microstructure of tempering parameters (a)(b)(c)400°C for 15 mins, 30 mins & 60mins, (d)(e)(f) 450°C for 15 mins, 30 mins & 60mins,(g)(h)(i) 500°C for 15 mins, 30 mins & 60mins.

3.3. Design of Experiments The DoE is a powerful statistical approach in optimizing the process parameter (Douglas (2009)). DoE is a useful tool in identifying a set of factors which have a significant influence to the process and finds at what levels the factors have to be maintained in order to optimize the process performance (Antony (2002)). To analyze the experimental results, the bulk hardness was obtained using Rockwell hardness tester and measured values were fed in the software. The bulk hardness was mainly taken into consideration as it is correlated with ultimate tensile strength and also fatigue strength. The experiment layout using L9 OA is given in the Table 3. Thus, bulk hardness is considered as the dominant response in tempering which decides the fatigue life of the component.