<p>The influence of hatch spacing on epitaxial grain growth and crystallographic texture evolution was investigated in flat-top laser powder bed fusion (LPBF) of a Ni–8Al superalloy. Laser scanning was performed bidirectionally with alternating hatch directions (HDs) of 0 deg and 90 deg between layers, forming droplet-shaped melt pools. At the melt pool center, grains grew epitaxially from the flat pool bottom along the build direction (BD). In the lateral–tail regions, grains followed trajectories inclined ~ 45 deg toward the melt pool center in the scan direction (SD) and ~ 45 deg upward toward the BD. A small hatch spacing promoted epitaxial growth from a melt pool side toward the center. This mode was associated with ± 45 deg rotations about a <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$\langle 110\rangle$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">⟨</mo> <mn>110</mn> <mo stretchy="false">⟩</mo> </mrow> </math></EquationSource> </InlineEquation> axis parallel to the BD, induced by the bidirectional scanning. Consequently, a dominant <InlineEquation ID="IEq2"> <EquationSource Format="TEX">$\langle 110\rangle$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">⟨</mo> <mn>110</mn> <mo stretchy="false">⟩</mo> </mrow> </math></EquationSource> </InlineEquation> texture developed along the BD, accompanied by a strong <InlineEquation ID="IEq3"> <EquationSource Format="TEX">$\langle 111\rangle$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">⟨</mo> <mn>111</mn> <mo stretchy="false">⟩</mo> </mrow> </math></EquationSource> </InlineEquation> texture along the SD and HD. As the hatch spacing increased, deflection caused by the lateral boundary of the adjacent melt pool diminished. This reduction favored <InlineEquation ID="IEq4"> <EquationSource Format="TEX">$\langle 100\rangle$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">⟨</mo> <mn>100</mn> <mo stretchy="false">⟩</mo> </mrow> </math></EquationSource> </InlineEquation>-oriented epitaxial growth along the BD, increasing the <InlineEquation ID="IEq5"> <EquationSource Format="TEX">$\langle 100\rangle$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">⟨</mo> <mn>100</mn> <mo stretchy="false">⟩</mo> </mrow> </math></EquationSource> </InlineEquation> texture intensity and decreasing the <InlineEquation ID="IEq60"> <EquationSource Format="TEX">$\langle 110\rangle$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">⟨</mo> <mn>110</mn> <mo stretchy="false">⟩</mo> </mrow> </math></EquationSource> </InlineEquation> texture intensity. On the SD/HD–BD plane, texture components dispersed. These results indicated that the hatch spacing regulates the melt pool interaction and the epitaxial growth continuity, thereby governing crystallographic texture evolution in flat-top LPBF.</p>

Epitaxial Grain Growth and Texture Evolution Controlled by Hatch Spacing in Flat-Top Laser Powder Bed Fusion of a Ni–8Al Superalloy

期刊论文
出版模式：

开放获取
发表日期：

2026年7月31日

查看全文

Tomonori Kitashima,
Kohei Araake,
Hsieh Lee-Tang,
Makoto Watanabe

摘要

The influence of hatch spacing on epitaxial grain growth and crystallographic texture evolution was investigated in flat-top laser powder bed fusion (LPBF) of a Ni–8Al superalloy. Laser scanning was performed bidirectionally with alternating hatch directions (HDs) of 0 deg and 90 deg between layers, forming droplet-shaped melt pools. At the melt pool center, grains grew epitaxially from the flat pool bottom along the build direction (BD). In the lateral–tail regions, grains followed trajectories inclined ~ 45 deg toward the melt pool center in the scan direction (SD) and ~ 45 deg upward toward the BD. A small hatch spacing promoted epitaxial growth from a melt pool side toward the center. This mode was associated with ± 45 deg rotations about a $\langle 110\rangle$ $⟨ 110 ⟩$ axis parallel to the BD, induced by the bidirectional scanning. Consequently, a dominant $\langle 110\rangle$ $⟨ 110 ⟩$ texture developed along the BD, accompanied by a strong $\langle 111\rangle$ $⟨ 111 ⟩$ texture along the SD and HD. As the hatch spacing increased, deflection caused by the lateral boundary of the adjacent melt pool diminished. This reduction favored $\langle 100\rangle$ $⟨ 100 ⟩$ -oriented epitaxial growth along the BD, increasing the $\langle 100\rangle$ $⟨ 100 ⟩$ texture intensity and decreasing the $\langle 110\rangle$ $⟨ 110 ⟩$ texture intensity. On the SD/HD–BD plane, texture components dispersed. These results indicated that the hatch spacing regulates the melt pool interaction and the epitaxial growth continuity, thereby governing crystallographic texture evolution in flat-top LPBF.