Investigating the microstructure and mechanical properties of pulsedNd:YAG laser welding of Monel ۴۰۰ to Nimonic ۷۵

In this study, non-homogenous welding of nimonic ۷۵ superalloy to Monel ۴۰۰ with ۱mm thickness was investigated with pulsed Nd:YAG laser welding. The mechanicalproperties of the joint were analyzed with optical and scanning electron microscope, Xray diffraction, micro-hardness test and tensile test. In the case of non-homogeneouswelding of Nimoinc ۷۵ superalloy to Monel ۴۰۰, defects such as liquation cracks andporosity in the welded samples were observed. these defects were removed withincreasing the preheating temperature and decreasing the heat input. The results showedthe voltage, pulse width, pulse frequency and welding speed should be selected as ۵۰۰volts, ۹ milliseconds, ۳ Hz and ۰.۹ mm/s respectively to reach the proper penetrationdepth. Also, the investigations show that the welding structure is composed of austeniticmatrix containing columnar dendrites and some cellular areas. The mechanical propertiesof the weld metal were reduced after joining and segregation causes a change in theamount of elements and the appearance of intermetallic compounds in the spacesbetween dendrites and cells. All non-homogeneous samples broke during the tensile testfrom the weld metal area.

کلیدواژه ها:

Non-Homogeneous Pulsed Laser Welding ، Nimonic ۷۵ Superalloy ، Monel ۴۰۰ ، ColumnarAnd Coaxial Dendrites.