Effect of post-weld heat treatments on microstructure and mechanical properties of electron beam welded flow formed maraging steel weldment

Abstract

Seamless tubing of C-250 maraging steel manufactured by the flow forming technique was joined by the electron beam welding process. Various post-welding heat treatments were conducted to improve the overall mechanical properties of the welded tubing. For the 480uC/6 h/air cooling post-weld aging treated maraging steel, a significant increment of 11% reversion austenite was present in the weld metal. Only the tensile strength of this aging treated metal met the required specification while its percentage elongation reached only 50% of the specification, attaining only 35% of the strength of the parent metal. For the post-welded solutionzaging treated maraging steel, only the yield strength met the specification. Moreover, a significant amount of reversion austenite pools was also present at the grain boundaries of the material located at the weld metal. Although the homogenisation treatment could improve the hardness of the weld metal, it failed to have the tensile strength of the steel met the specification.

Enhancement of mechanical properties and failure mechanism of electron beam welded 300M ultrahigh strength steel joints

“…This could be due to the segregation of solutes and impurities at columnar dendritic grain boundaries and weld centerline. In FZ, during solidification, the cooling rate is sufficiently high and the fast-growing columnar grains push the solutes and impurities to the weld centerline and the boundary of columnar dendritic grains, this has been proved by previous studies [24][25][26][27]. Large columnar dendritic grain size in WM is equivalent to small grain boundary area.…”

Influence of aging temperature on strength and toughness of laser-welded T-250 maraging steel joint

“…Furthermore, the reverted austenite goes for retarding the diffusion of hydrogen to reduce the sensitivity of hydrogen embrittlement in the study of literature [28]. However, according to the researches, it is deemed that the reverted austenite is harmful to the toughness due to its inconsistent deformation with the matrix [12,17,29]. Therefore, the effect of reverted austenite has not been confirmed.…”

“…Its unique weldability in the solutionized condition followed by postweld aging treatments at a relatively low temperature makes itself attractive for fabrication of large welding structures [9,10]. In the present studies, maraging steel has been welded by several methods [11][12][13]. Gas tungsten arc welding is generally employed.…”

Current research and developments in welding of 18% nickel maraging steel

“…The most common among them are SA, HA, and HSA. [36][37][38] Figure 8 shows optical and SEM images of T-250 grade maraging steel, which depict the as-welded condition (a, b), aged BM (c, d), and the three different post-weld heat treated conditions DA (e, f), SA (g, h), and HSA (i, j). The precipitates, RA, and lath martensite are represented by 1, 2, and 3 in Figure 8.…”