Microstructural characterization of AISI 431 martensitic stainless steel coatings deposited by laser metal deposition

Additive manufacturing (AM) is increasingly viable for the high-volume production of complex parts due to material and time savings, weight reduction, design optimization, and the development of new materials. Laser metal deposition (LMD), a specific AM process, offers high build rates and larger deposition volumes, making it cost-effective for industries such as aerospace and defense, which benefit from increased productivity and the ability to repair large components. Martensitic stainless steels are valued for their mechanical properties in these sectors, despite the challenges of maintaining these properties during LMD deposition. The purpose of this study was to evaluate the deposition parameters for laser cladding using LMD with AISI 431 martensitic stainless steel powder and to analyze the morphological aspects. Microstructural evolution was assessed using optical and electron microscopy, with samples produced by varying laser power (800, 1000, 1400, 1600 W) and scanning speed (9, 14, 16 mm/s). The results showed dilution values between 10 and 27% for power values of 1400 and 1600 W for all laser beam velocities tested. Microstructural characterization revealed martensite and ferrite phases in the deposits. Increasing the scanning speed resulted in higher dilution and wettability and decreased the height/width ratio of the deposits. The laser deposition parameters also affected the solidification parameters (G/R) and the cooling rate (G x R), which are critical for understanding the resulting microstructure and hardness of the deposits. This study highlights the importance of considering geometric and microstructural aspects in LMD for AISI 431 steel to ensure high productivity and optimal performance and demonstrates the potential of the LMD process for the deposition of martensitic stainless steel.