Articles written in Sadhana

    • Experimental investigation of laser cladding of H13 hot work steel by Stellite 6 powderandiaoy


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      Cladding of metals can enhance the wear behavior of metals. Many dies work at elevated temperature such as hot forging dies and hot extrusion dies need resistance to wear at higher temperatures. In this article, the cladding of H13 hot work steel (DIN 1.2324) was investigated by laser cladding. The Stellite 6powders coat the steel surface by using a continuous fiber laser. Two important objects in cladding are the effect of laser process parameters on the quality of the cladding layer and the lateral overlapping percent in adjacent passes. The laser power, scanning speed, and powder feed rate are the process variables in the study. The results show that the laser power is the most influencing parameter and by increasing laser power and decreasing the scanning speed, the hardness and penetration depth of cladded powder in the substrate will be increased. The dilution factor increases by increasing the laser power and reducing scanning speed at a moderate powder feed rate. The microstructure observation shows that strong metallurgical bonding between the clad and substrate and good mixing of powder in substrate metal can be obtained by proper setting of process parameters. The microhardness of the cladded specimen increased to 300 HV (164% increase compared to the substrate material. Best results were obtained at 10% overlapping between adjacent irradiation passes.

    • Microstructural and mechanical investigation on fiber laser welding of S500MC steel


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      In recent decades, laser beam welding of high strength low alloy steel has replaced some other assembly processes used in the automotive, machinery, and agricultural equipment sectors. In this research, the effect of heat input on the microstructure and mechanical properties of the butt joint of high strength low alloy steel S500MC, which had been strengthened by thermomechanically controlled processing, was investigated. The joining process was performed in an autogenous mode at two different heat inputs (140 and 240 J/mm) using the laser beam welding process with a fiber source. Microstructural observations with an optical microscope and scanning electron microscope indicate that the microstructure of the fusion zone consists of acicular ferrite and scattered martensite packets. An increase in heat input reduced the contribution of martensite packets in the fusion zone. The presence of carbides in the coarse-grained heat affected zone created a fine martensitic packet moreover the packet size has increased with the higher heat input and the dissolution of carbides. Inaddition to the microstructural changes, the grain size in the weld zone and heat affected zone becomes larger than those observed in the base metal consequently, the properties resulting from the controlled thermomechanical treatment have been lost in both zone. This autogenous welding process produced a decrease in hardness in the fusion zone but an increase in local strength in the heat affected zone compared to the unaffected base metal. The tensile test confirmed that the fracture occurred within the mechanically weaker fusion zone. But at a high input of 240 J/mm due to the decrease volume fraction of martensite and coarse grain size, the strength of the fusion zone reaches 581 MPa, which shows a decrease of about 10% compared to the 140 J/mmheat input.

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