نوع مقاله : مقاله پژوهشی
نویسندگان
دانشگاه تهران
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
In this research, the effect of pulsed Nd:YAG laser welding variables, including pulse energy, frequency and welding speed, on the depth and width of Nimonic 75 with a thickness of 1 mm is investigated. The microstructure of the weld contains columnar grains in the border and coaxial grains in the center of the weld. At the welding boundary, the thermal gradient (G) is higher and the grains grow against the direction of heat transfer. Liquidation crack is one of the welding defects in Nimonic 75, which is caused by the presence of brittle phases of MC carbides such as TiC and also thermal stresses. By increasing the pulse time width and frequency, the average power and overlapping of pulses have been increased to reduce the temperature gradient and thus reduce the thermal stress on the weld. The microhardness in the weld was higher than the base metal and its value is different across the weld due to the change in microstructure. Liquidation cracks were observed in all the worked and heat-treated samples. By reducing the thermal stresses and performing the preheating process in all the tests, the length of the melting cracks decreased compared to the initial base plate. The preheating operation at 150 degrees Celsius removed the liquidation cracks.
کلیدواژهها [English]
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