Papers by Amirreza Farnia
Effect of welding mode and filler metal on microstructure and mechanical properties of dissimilar joints of S900MC thermomechanical steel to St52 carbon steel welded by gas tungsten arc welding
Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering
In this research, S900MC thermomechanical steel was jointed to St52 carbon steel through a gas tu... more In this research, S900MC thermomechanical steel was jointed to St52 carbon steel through a gas tungsten arc welding process in the continuous and pulsed modes. The welding was performed in two different weld designs of V-groove and close square, with and without using an ER70S filler metal, respectively. Furthermore, the microstructure, hardness, and tensile strength of the joints were investigated. A bainitic microstructure was observed in the weld metal of the samples jointed in the continuous mode. While the weld metal microstructure of the pulsed joints was changed from a ferritic microstructure to a tempered martensitic microstructure by implementing filler metal in the V-groove weld design. In all joints, the heat-affected zone was narrower at the S900M side and had a fine bainitic microstructure. Among all joints, the maximum hardness of 389 HV was achieved for the weld metal of V-groove joints welded in the pulsed mode. At a normal strain rate, there was no considerable cont...
Investigation of weldability of Ni-based superalloy Inconel 713LC
Microstructural, hardening, and wear characteristics of surface re-melted AISI 410S stainless steel via fiber laser process
Journal of Mechanical Science and Technology
The effect of thermal frequency and current amplitude on weldability, microstructural evolution and mechanical properties of AA7075 alloy joint in DP-GMAW process
The International Journal of Advanced Manufacturing Technology
Microstructure and mechanical properties of low power pulsed Nd:YAG laser welded S700MC steel
Sādhanā
Abrasive Wear Behavior and Its Relation with the Macro-indentation Fracture Toughness of an Fe-Based Super-Hard Hardfacing Deposit
Tribology Letters
Macro-indentation fracture mechanisms in a super-hard hardfacing Fe-based electrode
Engineering Failure Analysis
Effect of Ta on the microstructure and hardness of Stellite 6 coating deposited by low power pulse laser treatments
Surface and Coatings Technology, 2012
ABSTRACT Stellite 6 hardfacing alloy with different Ta contents is successfully synthesized with ... more ABSTRACT Stellite 6 hardfacing alloy with different Ta contents is successfully synthesized with an in situ process on low carbon ferritic steel substrate by Nd:YAG pulsed laser cladding with pre-placed Stellite 6 and Ta mixed powders. The effect of different amounts of Ta on the microstructure of the Stellite 6 hardfacing alloy is investigated using scanning electron microscopy, energy dispersive spectroscopy and transmission electron microscopy. With an increase in Ta content, in addition to orthorhombic Cr-rich M7C3 carbides observed in the Ta-free Stellite 6 alloy in interdendritic regions, Ta-rich M4C3.04 type carbides are formed as well as individual bulky Ta-rich MC type carbides in Chromium carbide–Cobalt solid solution eutectic area. Furthermore, the Co-rich dendrites become much finer. With further increase of Ta, hexagonal M7C3 carbides are formed at the interface of orthorhombic ones. These microstructural changes are responsible for the improvement of the hardness of the Ta modified Stellite 6 hardfacing alloy.
Effects of pulse duration and overlapping factor on melting ratio in preplaced pulsed Nd:YAG laser cladding
Optics and Lasers in Engineering, 2013
ABSTRACT Melting ratio is known as a suitable factor to illustrate the effects of process paramet... more ABSTRACT Melting ratio is known as a suitable factor to illustrate the effects of process parameters on the clad profile in order to provide a proper process design. However, the definition of melting ratio based on continuous irradiation of energy does not accommodate for pulse parameters. Hence, in order to study the effects of pulse parameters, such as pulse duration and overlapping factor, the definition of melting ratio is restated for pulsed laser process based on energy density concept. Carbon steel was cladded with Stellite 6 by scanning a 400 W pulsed Nd:YAG laser over a preplaced layer of powder paste. The results show that the trends of clad profiles variations can be explained using the restated definition. The results also show two different ranges for the effects of pulse duration and overlapping factor on melting ratio.
International Journal of Materials Research, 2011
Tantalum-modified Stellite 6 thick coatings: microstructure and mechanical performance
Journal of Materials Science, 2013
ABSTRACT Thick Co-based coatings with different contents of tantalum were prepared by simultaneou... more ABSTRACT Thick Co-based coatings with different contents of tantalum were prepared by simultaneous powder feeding laser cladding technique on 304 stainless steel substrate, with the Ta wt% being 0, 2, 7 and 12. Laser processing was carried out with a continuous 3.3 kW Yt:YAG fiber laser. Microstructural observations were executed using scanning electron microscopy, energy dispersive X-ray spectroscopy analysis, and transmission electron microscopy. Observations indicated that, with an increase in the Ta contents, the Ta-rich MC-type carbides were formed in interdendritic regions. Also, hexagonal M7C3-type carbides were formed instead of orthorhombic M7C3-type carbides. The orientation relationships between different phases and the matrix were determined by electron diffraction. Mechanical properties were determined using microhardness measurement at room temperature and wear resistance measurement at room and elevated (500 °C) temperatures. The research demonstrated that alloying any amount of tantalum, in spite of increasing the microhardness, could be detrimental for increasing the wear resistance of Stellite 6, both at room and elevated temperatures. The relationship between microstructure and mechanical properties is explained.
Microstructural characterization of Co-based coating deposited by low power pulse laser cladding
ABSTRACT A detailed microstructural study of Stellite 6 coating deposited on a low carbon ferriti... more ABSTRACT A detailed microstructural study of Stellite 6 coating deposited on a low carbon ferritic steel substrate using preplaced powder method and low power Nd:YAG pulse laser is performed. The grain structure and solidification texture of the coating are investigated by orientation imaging microscopy (OIM) and scanning electron microscopy. In addition, the effect of consecutive pulses on the microstructure of the coating is examined. The orientation relationship (OR) at coating/substrate interface and the solid state phase transformation in heat-affected zone are studied as well as the Vickers microhardness profile measurement in order to support the microstructural observations. An important conclusion is reached that the shape of solidification front during pulsed laser cladding is similar to the shape of solidification front during continuous cladding with a doubled laser beam scanning speed. Further, OIM reveals the Greninger-Troiano OR between the face centered cubic coating and bcc substrate grains. It is concluded that at the moment of solidification epitaxial growth of the grains in the coating occur on the austenitic grains of the substrate and that an austenite-ferrite transformation occurs in the heat-affected zone upon subsequent cooling.
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Papers by Amirreza Farnia