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Metal additive manufacturing (AM) is a layer-by-layer process that makes the direct manufacturing of various industrial parts possible. This method facilitates the design and fabrication of complex industrial, advanced, and fine parts that are used in different industry sectors, such as aerospace, medicine, turbines, and jewelry, where the utilization of other fabrication techniques is difficult or impossible. This method is advantageous in terms of dimensional accuracy and fabrication speed. However, the parts fabricated by this method may suffer from faults such as anisotropy, micro-porosity, and defective joints. Metals like titanium, aluminum, stainless steels, superalloys, etc., have been used—in the form of powder or wire—as feed materials in the additive manufacturing of various parts. The main criterion that distinguishes different additive manufacturing processes from each other is the deposition method. With regard to this criterion, AM processes can be divided into four classes: local melting, sintering, sheet forming, and electrochemical methods. Parameters affecting the properties of the additive-manufactured part and the defects associated with an AM process determine the method by which a certain part should be manufactured. This study is a survey of different additive manufacturing processes, their mechanisms, capabilities, shortcomings, and the general properties of the parts manufactured by them. [ABSTRACT FROM AUTHOR]

Laser cladding and subsequent isothermal holding were employed to fabricate the Fe-based nanobainitic coatings. The microstructures of the isothermal heat treated coatings were observed and characterized by using the optical microscope (OM), filed-emission scanning electron microscope (FE-SEM), field-emission transmission electron microscope (FE-TEM), energy-disperse X-ray spectroscopy (EDAX), and X-ray diffraction (XRD). The results showed that the elements of Mn, Cr, and Si segregated at the prior austenite interdendritic regions. The segregation of the solutes significantly affected on the kinetics of the nanobainitic transformation and the final microstructures obtained at the different isothermal temperatures. The bainitic transformation incubation time was reduced by the increasing of available driving force for nucleation. The bainitic sheaves grow across the interdendritic regions of the prior austenitic dendrites. The continuity and thickness of blocky austenite distributed at the prior interdendritic regions were sensitive to the transformation temperature, as a result of the threshold of the bainitic transformation varied with the chemical gradients near the segregated interdendritic regions. [ABSTRACT FROM AUTHOR]