The Latest Trends in Laser Powder Bed Fusion Technology

Laser powder bed fusion (L-PBF) is a metal additive manufacturing technology that directly manufactures complex three-dimensional parts by melting metal powder layer by layer with a high-energy laser beam. Its core process includes computer-aided design (CAD) model slicing, powder spreading, laser selective melting and layer-by-layer stacking, which ultimately forms a near-net-shape component without the need for traditional molds, significantly shortening the production cycle and reducing costs. The ultra-fine microstructure formed by rapid cooling of this technology gives the parts excellent mechanical properties.

Alloy Powders Products List

• High-Temperature Alloy Powders
• Stainless Steel Powders
• Precision Alloy Powders
• High-Entropy Alloy Powders
• Other Alloy Powders

The L-PBF process is divided into five steps:

1. Powder spreading: The coater spreads the metal powder evenly on the substrate or the previous solidified layer (the layer thickness is usually 20-100μm);

2. Laser scanning: The high-energy laser scans the powder layer according to the CAD slicing path to form a molten pool and quickly solidify;

3. Layer-by-layer stacking: The build platform descends layer by layer, and the powder spreading and scanning are repeated until the part is completed;

4. Inert gas protection: The entire process is carried out in an inert environment such as argon to prevent metal oxidation;

5. Post-processing: Remove unmelted powder and perform heat treatment or surface polishing if necessary.

L-PBF mainly includes three types of branch technologies:

Selective laser melting (SLM): completely melts powder, suitable for high-density parts;

Direct metal laser sintering (DMLS): partially melts powder particles and retains some sintering characteristics;

Electron beam melting (EBM): uses electron beam instead of laser, suitable for high-temperature materials such as titanium alloy.

Application areas

Technological Progress and Process Optimization

Multi-laser parallel processing: 4-8 lasers are used for synchronous scanning to expand the build chamber size to 600×600×600 mm³, and the production efficiency is increased by 300%;

Remelting technology: scan the same area twice to reduce porosity (down to <0.2%), improve density and surface finish;

Checkerboard partition scanning: reduce residual stress and reduce part deformation.

High entropy alloys: Alloys such as CoCrFeMnNi achieve high strength (>1 GPa) and corrosion resistance through L-PBF, and are used for parts in extreme environments;

High-strength aluminum alloys: AlSi10Mg has a tensile strength of 400 MPa after process optimization, and is used for lightweight automobiles;

Refractory metals and magnetic materials: Tungsten parts have a density of >98% (to solve the cracking problem), and soft magnetic alloys (such as Fe-Si) are used for high-efficiency motors.

Innovation of Key Materials

Stainless steel powder: 316L stainless steel is widely used in the biomedical field, with a compressive strength of up to 1340 MPa and a hardness of 206 BHN (Brinell hardness). Wear resistance and mechanical properties can be significantly improved by optimizing laser parameters (such as power and scanning speed). For example:

Layer thickness control: When the layer thickness is ≤20 μm, the printing density is ≥99.5%; if the layer thickness increases, the performance of different powders varies significantly (such as gas atomized powder is better than water atomized powder).

Influence of powder properties: Powder fluidity, bulk density and particle size distribution directly affect the morphology and density of the melt pool. Powders with poor fluidity are prone to defects and need to be accurately evaluated by equipment such as the FT4 rheometer.

Corrosion performance optimization: Microstructural differences in powders from different suppliers (such as oxide precipitation distribution) can change corrosion resistance. Studies have shown that specific powders can avoid intergranular corrosion and are suitable for in vivo implants.

Inconel alloy powder: L-PBF printing of Inconel 625/718 high-temperature alloy achieves fine-grained structure and excellent mechanical properties:

Interface property research: Multi-material connection (such as 316L/Inconel 718) needs to solve the interface cracks caused by the difference in thermal expansion coefficient. Stress concentration can be alleviated by the functional gradient material (FGM) transition layer.

Process efficiency breakthrough: The multi-laser system (four lasers in parallel) increases the construction rate of Inconel 625 to 14 cm³/h.

Powder reuse: The oxygen content of Inconel 718 powder increases after reuse, resulting in increased porosity and reduced ductility (yield strength increases but elongation at break decreases).

Titanium alloy powder: TC4/TA15/TC21 titanium alloy is prepared by EIGA (electrode induction melting gas atomization) method:

Low oxygen content and high fluidity: The oxygen content can be controlled at 0.08–0.12%, the fluidity is 22–24 s/50g, and the bulk density is 2.7–2.8 g/cm³.

Microstructure and properties: The printed part is composed of α' martensite and basket structure, with a tensile strength of 1150 MPa. The particle size range (50–180 μm) affects the stability of the molten pool, and fine particles (<50 μm) are prone to unfused defects.

Industrial Applications and Challenges

Large-caliber engine components are manufactured by LPBF, using gradient material design: nickel-based alloys (such as Inconel 718) are used in high-temperature areas, and titanium alloys (Ti6Al4V) are used in low-temperature areas to achieve local performance customization. The core challenge of multi-material printing lies in the mismatch between interface bonding strength and thermal expansion coefficient, and laser parameters (power 200-300W, layer thickness 30μm) need to be precisely controlled to avoid cracks.

LPBF can manufacture porous titanium alloy (Ti6Al4V/β-Ti) bone implants. The design of porosity 60%-80% and pore size 300-800μm promotes bone cell growth and accelerates bone integration. The porous structure reduces the elastic modulus to 3-5 GPa, which is close to human bone (10-30 GPa), reducing the stress shielding effect. Clinical cases show that the bone growth rate after customized acetabular cup implantation is 40% higher than that of traditional products. However, residual unmelted powder on the surface may cause inflammation, requiring forced sandblasting and acid pickling.

316L stainless steel is an ideal material for surgical forceps and bone drills due to its high hardness (HRC 30-35) and corrosion resistance. The surface roughness of 316L tools formed by LPBF (Ra=5-10μm) needs to be reduced to Ra<1μm by roller polishing to meet sterilization requirements. In the field of dentistry, 316L is used for removable partial denture brackets, and its yield strength (500±20 MPa) exceeds that of casting technology (400 MPa).