<p>Pure iron offers intrinsic biocompatibility for biodegradable orthopedic implants, addressing limitations of permanent metallic devices including stress shielding and secondary surgery requirements. Laser powder bed fusion (L-PBF) enables fabrication of complex cellular architectures essential for matching bone mechanical properties and accelerating biodegradation through increased surface area. However, systematic processing-structure-property relationships for L-PBF pure iron remain underdeveloped, requiring comprehensive parametric sensitivity analysis to establish optimal processing conditions for biomedical implant design. This work presents a systematic exploratory study as the foundational phase of a biomedical implant development program. A comprehensive parameter screening involving 144 specimens was conducted, systematically varying scanning speeds (500-1000mm <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$\text {s}^{-1}$</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mtext>s</mtext> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msup> </math></EquationSource> </InlineEquation>), spot sizes (110-170<InlineEquation ID="IEq2"> <EquationSource Format="TEX">$\upmu \text {m}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">μ</mi> <mtext>m</mtext> </mrow> </math></EquationSource> </InlineEquation>), and hatch spacings to evaluate their individual and combined effects on porosity, hardness, and geometric fidelity. Statistical analysis identified scanning speed as the dominant processing parameter, with systematic exploration revealing robust processing windows at volumetric energy density (<InlineEquation ID="IEq3"> <EquationSource Format="TEX">$E_v$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>E</mi> <mi>v</mi> </msub> </math></EquationSource> </InlineEquation>) = 47–55J mm<InlineEquation ID="IEq4"> <EquationSource Format="TEX">$^{-3}$</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mrow /> <mrow> <mo>-</mo> <mn>3</mn> </mrow> </mmultiscripts> </math></EquationSource> </InlineEquation> and energy intensity (<i>Ei</i>) = <InlineEquation ID="IEq5"> <EquationSource Format="TEX">$1.6 \times 10^{4}- 2.6 \times 10^{4}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>1.6</mn> <mo>×</mo> <msup> <mn>10</mn> <mn>4</mn> </msup> <mo>-</mo> <mn>2.6</mn> <mo>×</mo> <msup> <mn>10</mn> <mn>4</mn> </msup> </mrow> </math></EquationSource> </InlineEquation> J mm<InlineEquation ID="IEq6"> <EquationSource Format="TEX">$^{-2}$</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow /> <mrow /> <mrow> <mo>-</mo> <mn>2</mn> </mrow> </mmultiscripts> </math></EquationSource> </InlineEquation>, achieving porosity below 1% and hardness exceeding 140HV. Microstructural characterization revealed hierarchical grain structures with pronounced elongation (aspect ratio 2.16) and average grain size of 17.95 <InlineEquation ID="IEq7"> <EquationSource Format="TEX">$\upmu \text {m}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">μ</mi> <mtext>m</mtext> </mrow> </math></EquationSource> </InlineEquation> ± 11.56<InlineEquation ID="IEq8"> <EquationSource Format="TEX">$\upmu \text {m}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">μ</mi> <mtext>m</mtext> </mrow> </math></EquationSource> </InlineEquation>. Tensile testing yielded ultimate tensile strength of 472–482 MPa, validating the established processing-property correlations. This exploratory framework establishes the essential processing parameter relationships and optimal parameter ranges required for subsequent cellular structure development and biodegradation assessment phases, providing the foundational knowledge to advance pure iron’s viability for temporary orthopedic applications.</p>

A comprehensive bulk parametric study for additive manufacturing of pure iron via laser powder bed fusion

期刊论文
发表日期：

2025年11月17日

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Pedro Lopes,
José Silva,
Leonardo Santana,
João Castro,
João R. Matos,
Luís Garrido,
Catarina Costa,
Luís Oliveira,
Jorge L. Alves

摘要

Pure iron offers intrinsic biocompatibility for biodegradable orthopedic implants, addressing limitations of permanent metallic devices including stress shielding and secondary surgery requirements. Laser powder bed fusion (L-PBF) enables fabrication of complex cellular architectures essential for matching bone mechanical properties and accelerating biodegradation through increased surface area. However, systematic processing-structure-property relationships for L-PBF pure iron remain underdeveloped, requiring comprehensive parametric sensitivity analysis to establish optimal processing conditions for biomedical implant design. This work presents a systematic exploratory study as the foundational phase of a biomedical implant development program. A comprehensive parameter screening involving 144 specimens was conducted, systematically varying scanning speeds (500-1000mm $\text {s}^{-1}$ $s^{- 1}$ ), spot sizes (110-170 $\upmu \text {m}$ $μ m$ ), and hatch spacings to evaluate their individual and combined effects on porosity, hardness, and geometric fidelity. Statistical analysis identified scanning speed as the dominant processing parameter, with systematic exploration revealing robust processing windows at volumetric energy density ( $E_v$ $E_{v}$ ) = 47–55J mm $^{-3}$ $^{- 3}$ and energy intensity (Ei) = $1.6 \times 10^{4}- 2.6 \times 10^{4}$ $1.6 \times 10^{4} - 2.6 \times 10^{4}$ J mm $^{-2}$ $^{- 2}$ , achieving porosity below 1% and hardness exceeding 140HV. Microstructural characterization revealed hierarchical grain structures with pronounced elongation (aspect ratio 2.16) and average grain size of 17.95 $\upmu \text {m}$ $μ m$ ± 11.56 $\upmu \text {m}$ $μ m$ . Tensile testing yielded ultimate tensile strength of 472–482 MPa, validating the established processing-property correlations. This exploratory framework establishes the essential processing parameter relationships and optimal parameter ranges required for subsequent cellular structure development and biodegradation assessment phases, providing the foundational knowledge to advance pure iron’s viability for temporary orthopedic applications.