Unravelling the origin of multiple cracking in an additively manufactured Haynes 230

Figures & data

Figure 1. Crack identifications in the SLMed Haynes 230 superalloy: (a) Low-magnification image showing the overall cracking status. (b) High-magnification images showing examples of a solid-state crack and a hot-crack (solidification crack). (c) Columnar charge showing the number fractions of the identified cracks and those unresolved cracks. (d, e) and (f, g) Correlated ECCI-EBSD images showing two cracked regions with three cracks numbered 1, 2 and 3; (h, i) High-magnification ECC images showing the microstructures centred on the crack 1 and 3, respectively, where film-like features are clearly observed.

Figure 2. TEM observations on the film-like phase: Bright field images showing (a) the overall view of the lift-out lamella sample and (b) the film-like phase enclosed to the crack. (c) High-resolution TEM image centred on the interface of the film-like phase and the matrix, with insets showing their FFT patterns, respectively. (d) STEM-HAADF image and the corresponding elemental maps centred on the crack tip and the carbide film.

Figure 3. Atom probe tomography on the M₂₃C₆ carbide: (a) APT reconstruction with a 4.0 at.% C iso-composition surface embedded in Ni atoms showing the presence of the carbide. (b) 2D elemental distribution maps in the orange region of interest. (c, d) 1D composition profiles along the black arrow in (b).

Figure 4. Combined experimental-thermo-calc investigation on the Mn, Si, Fe-free counterpart and the current Mn, Si, Fe-containing Haynes 230: (a) Columnar chart showing the measured crack density, with an inset showing the overall crack status in the Mn, Si, Fe-free counterpart; Thermo-calc simulation showing (b) the solidification path based on the Scheil-Gulliver assumption and (c) the equilibrium phase curve focusing on the M₂₃C₆, fcc and liquid phases, using the TTNI8 database.

Table 1. Standard composition range and also measured composition of the SLMed Haynes 230 superalloy (the current one with, and the modified one without Si, Mn, Fe, all in wt.%).

Haynes 230	C	B	Si	Mn	Fe	Mo	W	Cr	Al	Ni
Standard range	0.05–0.15	≤0.015	≤0.75	≤1.00	≤3.00	1.00–3.00	13.00–15.00	20.00–24.00	0.20–0.50	–
Current with Si, Mn, Fe	0.0658	0.0056	0.391	0.488	1.778	2.034	12.987	20.099	0.327	–
Modified Si, Mn, Fe-free	0.0703	0.0041	0.022	<0.005	0.049	1.955	13.569	21.989	0.432	–