Regarding 18Ni-300 maraging steel, Aging treatment resulted in a slightly better and more moderate fatigue behaviour according to [71]. In another study, Herman Becker and Dimitrov [27] studied the effects of successive solution annealing and ageing on the FCG behaviour of this steel. According to their results, heat treated specimens had slightly higher ΔKth values and lower crack growth rate. In addition, the heat treatment eliminated the differences between the FCG behaviour of the specimens manufactured via single and double exposure methods. According to their evaluation, this similarity between FCG behaviour of samples manufactured via different scanning strategies may be attributed to relief of residual stresses after the heat treatment, since there was a significant difference between the average values of residual stresses in the samples made by single and double exposure methods in their as-built condition [27].