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<p>AISI 4340 steel was deposited using cold spray (CS) and laser-assisted cold spray (LACS) techniques at different surface temperatures of 500, 738, and 950&#xa0;°C. To study the microstructure evolution and phase transformation, scanning electron microscopy and x-ray diffraction were used on both the starting powders and the CS and LACS deposits. The dislocation density was determined by x-ray line profile analysis at the top and bottom of the CS and LACS deposits. It was found that the grain size, dislocation density, and hardness show significant differences between the top and bottom of the deposits at higher surface temperatures, such as 738 and 950&#xa0;°C. Laser heating at 500&#xa0;°C during the CS deposition reduced the dislocation density compared to the cold-sprayed steel sample without laser heating. Higher laser temperatures (738 and 950&#xa0;°C) resulted in significantly higher dislocation densities, which can be attributed to the strains caused by the martensitic phase transformation. The hardness variation up to 738&#xa0;°C reflects changes in dislocation density. At 950&#xa0;°C, the hardness is lower than expected due to grain growth compensating for the high dislocation density.</p>

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Evolution of Defects and Microstructure in AISI 4340 Steel Produced by Laser-Assisted Cold Spray Deposition

  • 期刊论文

  • 发表日期：

    2025年11月19日

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  • Anita Heczel,
  • Dallin J. Barton,
  • Jenő Gubicza,
  • Luke N. Brewer

摘要

AISI 4340 steel was deposited using cold spray (CS) and laser-assisted cold spray (LACS) techniques at different surface temperatures of 500, 738, and 950 °C. To study the microstructure evolution and phase transformation, scanning electron microscopy and x-ray diffraction were used on both the starting powders and the CS and LACS deposits. The dislocation density was determined by x-ray line profile analysis at the top and bottom of the CS and LACS deposits. It was found that the grain size, dislocation density, and hardness show significant differences between the top and bottom of the deposits at higher surface temperatures, such as 738 and 950 °C. Laser heating at 500 °C during the CS deposition reduced the dislocation density compared to the cold-sprayed steel sample without laser heating. Higher laser temperatures (738 and 950 °C) resulted in significantly higher dislocation densities, which can be attributed to the strains caused by the martensitic phase transformation. The hardness variation up to 738 °C reflects changes in dislocation density. At 950 °C, the hardness is lower than expected due to grain growth compensating for the high dislocation density.