376HV & 57.1% Grain Boundary! Breakthrough in Superalloy LPBF

Home > Materials

October 24, 2025 Materials 153

Annular laser beam LPBF enhances IN939 superalloy quality by stabilizing the melt pool and reducing defects compared to Gaussian beam.

Laser Powder Bed Fusion (LPBF) has become a key manufacturing process in the aerospace sector due to its outstanding advantages in shaping complex structures and material utilization. However, traditional Gaussian beams, limited by their uneven energy distribution and spot size, often lead to unstable forming quality and insufficient process reliability when processing difficult-to-machine superalloys like IN939. According to news from Nanjixiong, AVIC MT and Shandong University have jointly tackled these challenges, systematically conducting research on forming IN939 alloy using annular laser beam LPBF, thereby providing a new process route for the additive manufacturing of aerospace high-temperature components.

The study focused on IN939 nickel-based superalloy. By using beam shaping technology to convert the traditional Gaussian beam into an annular beam, the researchers systematically compared and analyzed the melt pool behavior, grain orientation, texture characteristics, surface quality, and mechanical properties of IN939 alloy formed by LPBF under the two beam types from both experimental and simulation perspectives, revealing the intrinsic relationship between beam morphology and alloy microstructure evolution.

LPBF-formed IN939 metallography and defect proportion statistics under different process conditions for Gaussian and annular beams.

Melt pool morphology of LPBF-formed IN939

The results show that for LPBF forming of IN939 nickel-based superalloy, the annular beam demonstrated a wider process window compared to the Gaussian beam. No keyhole defects were found even at high scanning speeds and large hatch spacings. The melt pool depth-to-width ratio significantly decreased from 0.46 to 0.14, and the heat transfer mode shifted from the keyhole mode to the more stable conduction mode. Under identical process conditions, IN939 samples formed with the annular beam exhibited superior microstructural properties: the proportion of low-angle grain boundaries reached 57.1% (compared to only 28.1% with the Gaussian beam), significantly reducing the cracking tendency, and the Vickers hardness increased to 376.92 HV. Simultaneously, the annular beam promoted more sufficient metallurgical bonding between melt tracks, reduced the surface roughness of the formed samples from 5.8 μm to 4.0 μm, lowered the melt pool temperature gradient, decreased the peak flow velocity by 37%, stabilized melt pool flow, and effectively suppressed spattering, achieving a significant improvement in surface quality.

The research findings were published as a cover article in the authoritative Chinese aerospace manufacturing journal Aeronautical Manufacturing Technology, Vol. 68, No. 20, 2025, under the title "Research on Microstructure Control of IN939 Nickel-based Alloy Formed by Annular Laser Powder Bed Fusion." The work was completed by the team of Professor Han Quanquan from Shandong University and the team of Dr. Gao Zhengjiang from AVIC MT.

AVIC MT was deeply involved throughout the research project, providing crucial forming equipment and materials. Furthermore, leveraging their engineering experience, they offered technical support for research plan formulation and process parameter optimization.

The project utilized the AVIC MT MT280 LPBF equipment, equipped with an adjustable beam shaping module that successfully converted a 70μm Gaussian beam into a 167μm annular beam. Paired with a 500W dual-laser system, it provided stable support for the project. This equipment, with a build size of 265×265×400 mm, is suitable for scientific research, teaching, training, competitions, and small-batch manufacturing. It served as the sole designated metal 3D printer for the Beijing赛区of the 47th WorldSkills Competition and has supported scientific innovation in numerous universities and research institutes.

The MT-IN939 nickel-based superalloy powder used in the project was independently developed by AVIC MT. The powder was prepared using Vacuum Induction Melting - Gas Atomization (VIGA) technology, featuring uniform composition, concentrated particle size distribution (15–53 μm), and advantages such as excellent high-temperature strength, outstanding corrosion resistance, and significant thermal fatigue resistance. This effectively supported the efforts in microstructure control and crack inhibition during laser forming.

Focusing on innovation in metal additive manufacturing equipment, material technology, and product services, AVIC MT continuously empowers future talent development and exploration of cutting-edge industrial technologies. Through their independently developed high-performance metal powder materials (such as superalloys, aluminum alloys, and titanium alloys), the MT170/MT17H/MT280 series of metal 3D printing equipment, and advanced atomization powder production technologies like AVI-PA/VIGA/PREP, AVIC MT has provided research support to numerous universities and institutes including Zhejiang University, Sichuan University, Tianjin University, South China University of Technology, Shandong University, and Beijing University of Technology, facilitating numerous innovative research projects.

In the future, AVIC MT will continue to deepen its integrated innovation capabilities in metal additive manufacturing materials and equipment. They aim to collaborate with more universities and research institutes to build a industry-university-research collaborative innovation system, assist in the implementation and industrial translation of high-level scientific research achievements, and continually contribute to the development of the additive manufacturing industry.