Selective laser melting of iron-based powder

Selective laser melting of iron-based powder

Accepted 14 November 2003 | J.P. Kruth, L. Froyen, J. Van Vaerenbergh, P. Mercelis, M. Rombouts, B. Lauwers
This paper discusses the selective laser melting (SLM) of a mixture of iron, nickel, copper, and iron phosphide (Fe, Ni, Cu, and Fe3P) to produce near full-density objects with mechanical properties comparable to bulk materials. Unlike selective laser sintering (SLS), SLM involves complete melting of powder particles, which can lead to issues such as balling, residual stresses, and deformation. The study focuses on optimizing the process parameters and scanning strategies to minimize these issues. Key findings include: 1. **Thermal Deformations**: The temperature gradient mechanism (TGM) and varying process temperatures can cause thermal stresses that lead to part distortion and failure. Different scanning strategies, such as sector-wise scanning, were tested to reduce deformation. 2. **Wettability**: Balling, a phenomenon where molten material fails to wet the substrate, is mitigated by optimizing laser parameters to minimize the length-to-diameter ratio of the molten pool. High scan speeds and laser powers reduce balling. 3. **Vaporization Effect**: Pulsed laser operation mode can enhance interlayer connection and improve density by promoting evaporation, which reduces the balling effect. 4. **Mechanical Properties**: Parts produced with pulsed laser operation showed improved bending strength and density compared to continuous wave (CW) mode. The maximum bending strength of 630 MPa was achieved at a material density of 91%. The study emphasizes the importance of process parameter optimization and the use of appropriate scanning patterns to achieve high-quality SLM parts.This paper discusses the selective laser melting (SLM) of a mixture of iron, nickel, copper, and iron phosphide (Fe, Ni, Cu, and Fe3P) to produce near full-density objects with mechanical properties comparable to bulk materials. Unlike selective laser sintering (SLS), SLM involves complete melting of powder particles, which can lead to issues such as balling, residual stresses, and deformation. The study focuses on optimizing the process parameters and scanning strategies to minimize these issues. Key findings include: 1. **Thermal Deformations**: The temperature gradient mechanism (TGM) and varying process temperatures can cause thermal stresses that lead to part distortion and failure. Different scanning strategies, such as sector-wise scanning, were tested to reduce deformation. 2. **Wettability**: Balling, a phenomenon where molten material fails to wet the substrate, is mitigated by optimizing laser parameters to minimize the length-to-diameter ratio of the molten pool. High scan speeds and laser powers reduce balling. 3. **Vaporization Effect**: Pulsed laser operation mode can enhance interlayer connection and improve density by promoting evaporation, which reduces the balling effect. 4. **Mechanical Properties**: Parts produced with pulsed laser operation showed improved bending strength and density compared to continuous wave (CW) mode. The maximum bending strength of 630 MPa was achieved at a material density of 91%. The study emphasizes the importance of process parameter optimization and the use of appropriate scanning patterns to achieve high-quality SLM parts.
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