4.5. Comparisons of the residual stress
The maximum residual stresses of the quenched samples in the three sets of multi-stage quenching tests and the single-stage quenching test (S) are shown in Fig. 20. It can be observed that the maximum residual stresses of the single-stage quenched sam- ple (S) are obviously higher than the multi-stage quenched sam- ples. Besides, the difference between sample B and sample C is very small, which means that adopting the two kinds of spraying parameters at the initial stage cause almost equivalent residual stresses. Considering the experimental results in Section 4.3, it