Page 114 - ESAM-1-2

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

pores preferentially forming in these weakened regions. grain refinement strengthening, and carbide dispersion
42
In the HIP1100 specimen, hard carbides distributed strengthening.
along the grain boundaries were characterized by lower Compared to the pre-deformation condition, significant
ductility compared to the matrix, contributing to the carbide coarsening occurred along the grain boundaries in
desynchronized deformation between the carbides and the HIP1100 specimen during high-temperature tensile
the matrix. Moreover, the large-sized carbides among testing, while minimal changes were observed for the
the discontinuous carbides distributed along the grain HIP1180 and HIP1210 specimens. As the HIP temperature
boundaries induced localized stress concentrations, increased, the tensile strength and elongation both
39
making these coarse carbides potential weak regions. improved due to the synergistic effect of reduced number
Subsequently, cracks were prone to initiate within the bulk of grain boundaries and the chain-like distribution of
carbides and at grain triple junctions, propagating and carbides, reaching a maximum tensile strength of 236 MPa
20
forming intergranular fracture surfaces and secondary and elongation of 29.0% at HIP1210.
cracks extending along the grain boundaries. In addition,
compared to the HIP1180 and HIP1210 specimens, the Under room temperature tensile testing, the fracture
small-sized grains at HIP1100 resulted in a reduction surfaces exhibited typical ductile failure with numerous
in the number of grain boundaries, which further dimples. In contrast, during high-temperature tensile
exacerbated boundary weakening. This microstructural testing, the cracks primarily propagated along the grain
condition corresponded to reduced tensile strength boundaries, with the HIP1210 specimen exhibiting a better
and elongation, along with the formation of long cracks capacity for crack inhibition. Compared to the HIP1100
penetrating the specimens. On the contrary, when the and HIP1180 specimens, the massive feature presented on
HIP temperature increased to 1,180°C and 1,210°C, the the fracture surface of HIP1210 was more pronounced,
chain-like carbides along the grain boundaries enhanced demonstrating a typical characteristic of intergranular
the strength of the grain boundaries, inhibiting stress fracture.
concentrations. Moreover, the number of grain boundaries
decreased, thereby limiting crack propagation. As a Acknowledgments
22
result, the HIP1180 and HIP1210 specimens both achieved None.
improved tensile strength and elongation, attributed to the
synergistic effect of reduced number of grain boundaries Funding
and chain-like distribution of carbides. These specimens The research was supported by the National Natural
demonstrated fracture morphologies characterized by Science Foundation of China (No. 52475332) and the
wedge-shaped cracks and minor cracks, respectively. Taishan Scholars Foundation of Shandong Province (No.

4. Conclusion tsqn202211307).
The microstructure evolution and mechanical properties Conflict of interest
of LPBF-manufactured Hastelloy X alloy following various Dr. Swee Leong Sing is the Editor-in-Chief of this journal,
HIP treatments at both room and high temperatures were but was not in any way involved in the editorial and
investigated. When the HIP temperature increased from peer-review process conducted for this paper, directly or
1,100°C to 1,210°C, the recrystallization process gradually indirectly. Separately, other authors declared that they
progressed and achieved completion at 1,210°C. The have no known competing financial interests or personal
proportion of low-angle grain boundaries decreased from relationships that could have influenced the work reported
49.7% at HIP1100 to 4.3% at HIP1180, and eventually to in this paper.
0% at HIP1210. The carbides along the grain boundaries
transformed from particle distribution at HIP1100 to Author contributions
chain-like distribution at HIP1180, and coarse chain-like Conceptualization: Junjun Jiang
distribution at HIP1210. Data curation: Bingqiu Wang, Yiming Sun, Caiwang Tan
After the HIP treatments, the yield strength decreased, Formal analysis: Caiwang Tan
while the tensile strength and elongation increased Investigation: Bingqiu Wang
compared to the as-built specimen. As the HIP temperature Methodology: Rongrong Huang, Bo Chen, Caiwang Tan
increased, the elongation of the HIP specimens gradually Resources: Junjun Jiang
improved, reaching a maximum value of 45% at HIP1210. Supervision: Rongrong Huang, Bo Chen, Xiaoguo Song
The tensile strength declined, achieving a value of Validation: Linan Xue
774 MPa at HIP1100 due to restrained dislocation slip, Writing – original draft: Bingqiu Wang

Volume 1 Issue 2 (2025) 12 doi: 10.36922/ESAM025240015