Microstructural characterization martensitic stainless-steel coatings deposited by laser metal deposition

Abstract

Additive manufacturing (AM) technology, characterized by layer-by-layer deposition, is emerging as an alternative to produce parts, typically with complex geometries, and has recently become an option for mass production. This technology has been adopted by several industries due to its ability to save material resources and processing time. In addition, it could lead to component weight reduction, design optimization and the development of new materials. Among the AM processes, laser metal deposition (LMD) offers a high build rate and allows for larger deposition volumes compared to powder bed-based technology, resulting in lower manufacturing costs. Several industries, such as aerospace and defense, have focused on the use of LMD due to the opportunities for cost savings, increased productivity, and repair of large mechanical components. In particular, LMD could be used in the aerospace industry for the manufacture and repair of engines, turbines and propulsion systems, space shuttles, communications satellites. Currently, several types of metals, including important engineering materials such as steel, aluminum, and titanium, can be used to produce parts with high levels of precision and excellent properties. The use of martensitic stainless steels has increased in the automotive, aerospace and defense industries, mainly due to their mechanical properties such as high flow resistance and reasonable ductility. However, the deposition of martensitic stainless steels using LMD presents challenges in the selection of parameters, morphology configurations and phase evolutions to ensure the required mechanical properties. The objective of the present work was to evaluate the deposition parameters for laser cladding using LMD with martensitic stainless steel AISI 431 powder. In addition, morphological aspects were analyzed. The microstructural evolution was assessed using optical and electron microscopy. The results show dilution values between 10 and 27% were found for power values between 1400 and 1600 W and laser beam velocities of 9, 14 and 16 mm/s. Microstructural characterization revealed martensite and ferrite phases in the depositions. Several factors influence the geometric and microstructural characteristics of the laser cladded deposits, such as the morphology and size distribution of the filler particles, the chemical composition of the materials, the flow rate and deposition method of the filler, and the power and beam speed of the laser.