The Effect of Post-Weld Aging Treatments on the Microstructure, Texture, and Mechanical Properties of Grade 250 Maraging Steel Laser Weldments

In this paper, 250-grade maraging steel has been laser welded, and post-aging treatments have been done at 420, 480 and 540 °C. The effect of aging temperature on microstructural evolution, texture evolution, and mechanical properties has been investigated. The aging process has resulted in the appearance of a new phase, which takes the form of white pools. Austenite pools have been found to concentrate primarily at the boundaries of cells. A sizeable portion of the grains is aligned along 〈111〉/〈100〉. However, low-angle boundaries are found to be in the range of ≈ 63–73%. When the temperature of the aging process is 540 °C, very fine grains of equiaxed martensite, which are indicative of recrystallization, has been observed. The orientation distribution function of the lath martensite reveals the development of γ-fiber in the laser weld (LW) sample. LW420 reveals some average intensity cube (001) [0 \(\overline{1 }\) $\overline{1}$ 0] and copper (112) [ \(\overline{1 }\overline{1 }\) $\overline{1}\overline{1}$ 1] component. LW480 shows γ-fiber and near (001) [1 \(\overline{1 }\) $\overline{1}$ 0] and rotated cube (001) [ \(\overline{1 }\overline{1 }0\) $\overline{1}\overline{1}0$ ] components. However, LW540 reveals some average-intensity Copper (112) [ \(\overline{1 }\overline{1 }\) $\overline{1}\overline{1}$ 1], (111) [ \(1\overline{1 }\) $1\overline{1}$ 0] and (332) [ \(\overline{1 }\overline{1 }\) $\overline{1}\overline{1}$ 3] component. The tensile fracture surface of the samples, as laser weld and post-weld aging at 420, 480, and 540 °C, shows a dimple fracture surface with Al₂O₃ and TiO₂ inclusions. These inclusions may be responsible for inferior mechanical response in the case of laser welding. No apparent differences has been observed in the Taylor factor distribution between LW480 and LW540. However, in the case of LW540, the average Taylor factor value was 2.93, a relatively low value compared to the LW (3.11) sample. This indicates the major role of crystallographic texture on tensile properties.