| Nickel based alloy is widely used in energy chemical industry and marine development due to its good resistance to high temperature and corrosion.It is an economic and effective protection method to deposit nickel based alloy on the equipment by cladding.In case of cladding,a lower dilution ratio of the overlay is helpful to obtain better corrosion resistance.The CMT technology can realize cladding process with high efficiency and low dilution ratio.However,when depositing nickel based alloy,it will also cause problems such as poor formation due to bad fluidity.The TIG-CMT hybrid cladding can keep the characteristics of CMT as well as improve the cladding formation.In this paper,the process of Inconel 625 cladding using TIG-CMT hybrid heat sources is analyzed by numerical simulation.A simplified numerical simulation method of CMT droplet transfer process is proposed,and the influence of cladding parameters on the wettability and dilution ratio of the overlay is studied.First of all,the numerical analysis model of TIG-CMT hybrid cladding is established by VOF method,which takes into account the influence of droplet transfer,electromagnetic force,arc pressure and surface tension.The model can realize the free surface tracking,droplet loading and the implementation of boundary conditions such as heat sources and force sources.It lays the foundation for the numerical simulation and analysis of hybrid cladding process.Secondly,the characteristics of temperature field and fluid field in the process of CMT cladding and TIG-CMT hybrid cladding are compared and analyzed by numerical simulation.The results show that the variation of heat input mainly affects the area within 3mm around the weld bead center during CMT cladding.The increase of wire feeding speed mainly enhances the flow trend of liquid metal towards the rear of the weld pool,while it has less effect on the weld pool area on the substrate.The wettability of welding is poor.In the TIG-CMT hybrid cladding,when the TIG current reaches160A,the temperature of the area 3mm away from the weld bead center increases above150K.The temperature at the edge of the weld pool increases,and the temperature gradient of the substrate decreases.At the same time,the area of the weld pool increases,and the back flow effect of the weld pool is weakened.The preheating of TIG heat source is beneficial to the spread of nickel based alloy,which can improve the cladding formation.Finally,the effects of TIG-CMT hybrid cladding parameters on the cladding formation are studied.With the increase of TIG current,the temperature at the edge of the weld pool and the substrate increases.The flow field expands,the spread range of nickel based alloy increases,and the wettability improves gradually.With the increase of CMT current,the temperature in the weld pool increases.The velocity in front of the weld pool increases,the melting area on the substrate increases,and the dilution ratio increases.With the increase of welding speed,the cooling rate and temperature gradient of the substrate increase.The area and velocity of weld pool decrease,and the weld width and melting area of substrate decrease.When TIG current is 160A and welding speed is 10mm·s-1,the dilution ratio is between?3%and?5%under different CMT current.When CMT current is greater than 205A,the contact angle of the overlay is less than 90°. |
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