Page 105 - ESAM-1-2

Engineering Science in
Additive Manufacturing HIP temperature effects on LPBF Hastelloy X

characteristics were investigated, and mechanical 1,210°C were labeled as HIP1100, HIP1180, and HIP1210,
properties at room and high temperatures were tested respectively.
using failure mode analysis.
2.2. Material characterization
2. Experimental methods The test specimens were cut from the LPBF-manufactured
2.1. Materials and deposition process samples using wire electrical discharge machining, and
the cross-sections were mechanically polished to achieve a
The Hastelloy X superalloy powder utilized in this smooth mirror finish. Aqua regia (hydrochloric acid: nitric
experiment was gas atomized by Xi’an Bright Laser acid: 3:1) was used to etch the cross-sectional surfaces
Technologies Co., Ltd (China). The composition of of both the as-built and HIP specimens. The DSX510,
Hastelloy X superalloy powder is listed in Table 1. manufactured by Olympus Corporation (Japan), was
The SLM280 machine produced by Solution GmbH employed to observe the microstructural morphology and
in Germany was employed for LPBF. The laser focus defects. The ImageJ software (version 1.53) was used to
diameter ranged from 80 μm to 115 μm. The experimental statistically analyze the rate of pores and carbides within
process was conducted under the protection of nitrogen, a certain area.
maintaining the proportion of oxygen below 0.2%. The The Zeiss’s MERLIN Compact scanning electron
pre-heat temperature of the substrate was set to 150°C microscope (SEM; Germany) was used for high-
to reduce the temperature gradient during the LPBF magnification microstructure observation. Energy
process. Before the LPBF process, the Magic24 software dispersive spectroscopy integrated with the SEM was utilized
(version 24.0) was configured with the SLM280 to design for chemical composition analysis of the microstructure.
the three-dimensional model of test samples, followed After mechanical and electrolytic polishing to remove the
by importing the experiment parameters into SLM280 strain layer, electron backscattered diffraction (EBSD)
for setup. Based on the preliminary experiments, the integrated with SEM was employed for microstructure
experiment parameters for deposition were set at a laser characterization of the specimens. The TSL Orientation
power of 300W, scanning speed of 900 mm/s, and a layer Imaging Microscopy analysis software (version 7.0) was
rotation angle for scanning of 67°, as shown in Figure 1A.
used for the subsequent analysis of EBSD data.
The HIP treatment was conducted using the
The transmission electron microscopy (TEM) specimens
HIPEX850 HIP machine manufactured by CISRI HIPEX were extracted from the central region of the as-built and
Technology CO., LTD. (China). The HIP machine utilized HIP specimens. They were mechanically thinned to 60 μm
nitrogen as the pressure-transmitting medium, ensuring
uniform pressure application on the component surface. using sandpaper, followed by ion milling. The ThemisZ
According to the melting temperature of Hastelloy X alloy spherical aberration-corrected TEM (Tecnai G2 F30, US)
(1,295°C – 1,381°C), HIP treatments were performed at was used to analyze the substructure morphology and
1,100°C, 1,180°C, and 1,210°C, with a pressure of 160 MPa, element distribution within the specimens.
a holding time of three hours, and a ventilation cooling rate After the sample surfaces were polished, the hardness
of 4.5 K/min. The HIP specimens at 1,100°C, 1,180°C, and of cross-sections of the as-built and HIP specimens
Table 1. Chemical composition of Hastelloy X

Element Nickel Ferum Chromium Molybdenum Cobalt Carbon Tungsten Silicon Aluminum Titanium
Content (wt.%) Balance 18.86 21.16 9.78 2.20 0.067 0.62 0.037 0.028 <0.01

A B

Figure 1. Schematic of building specimens. (A) A schematic diagram of the scanning strategy by laser powder bed fusion. (B) The profile of the tensile test
specimen along the building direction.

Volume 1 Issue 2 (2025) 3 doi: 10.36922/ESAM025240015