Precipitation and austenite reversion behavior of a maraging steel produced by selective laser melting

Abstract

Abstract

Aging Behaviour and Mechanical Performance of 18-Ni 300 Steel Processed by Selective Laser Melting

“…From the present results (DSC scans and evolution of hardness during isothermal aging) it can be inferred that the solidification and cooling rates induced by SLM processing are fast enough to preserve the full aging potential of the 18-Ni 300 maraging alloy without any need to perform an additional post-SLM solution treatment. This result is in full agreement with the research work published by Jägle and coauthors [6]. By atom probe tomography, these researchers were able to show that, in a Co-containing maraging steel similar to the present alloy, no precipitates or clusters of atoms were present in the SLM as-built state, even considering that each layer had been subjected to significant reheating during the layer-by-layer manufacturing process.…”

“…From the present results (DSC scans and evolution of hardness during isothermal aging) it can be inferred that the solidification and cooling rates induced by SLM processing are fast enough to preserve the full aging potential of the 18-Ni 300 maraging alloy without any need to perform an additional post-SLM solution treatment. This result is in full agreement with the research work published by Jägle and coauthors [6]. By atom probe tomography, these researchers were able …”

“…Since holding at temperatures exceeding 500 • C is expected to promote extensive reversion of martensite into austenite in wrought maraging steels [1,3,[5][6][7][8][9], XRD and microstructural analyses were carried out to asses phase balance in the investigated samples. Figure 8 summarizes the XRD spectra acquired from samples treated according to different aging conditions, while quantitative evaluation of the γ-Fe phase fraction is reported in Table 2.…”

“…Aging leads to the formation of strengthening precipitates. It is reported that in the 18-Ni 300 alloy and in similar grades, the Ni 3 Ti phase (or more generally, Ni 3 X where X = Ti, Mo, V, and W) readily form on short-term aging at low temperatures (400-450 • C), followed by Fe 2 Mo or Fe 7 Mo 6 precipitation [1][2][3][4][5][6]. Aging at temperatures exceeding 500 • C concurrently promotes the formation of austenite by a diffusion-controlled reaction, which is also favoured by the release of Ni into the matrix due to decomposition of Ni 3 Ti phase [1,3,[5][6][7][8][9].…”

Precipitation Reactions in Age-Hardenable Alloys During Laser Additive Manufacturing

“…Since they form by precipitation phase transformations, they are called precipitates, and the materials featuring them, precipitation-strengthened alloys, 1 Examples are most Al alloys, [2][3][4] many Ni-based alloys [5][6][7] and some steels. [8][9][10][11] During conventional processing, these materials undergo two subsequent heat treatments. First, in a homogenization treatment in the single-phase region of the phase diagram, i.e.…”