Hastelloy C-276and316L Laser Dissimilar Welding Mechanism And Technology

As the depletion of the fossil energy and the contamination of the environment, the development of new energy has become an important part of the world development. The clean energy represented by nuclear energy has become the main research field by most of the developed countries. With characteristics of little dependence on nature and resource consumption, nuclear energy is paid more and more attention by every country. As the PWR (Pressurized Water Reactor) nuclear power unit of millon kilowatt, AP1000, which has the properties of high reliability and little requirence of maintance, is the most advanced unit with canned coolant pump. As the can is a main part of the coolant pump to prevent the leakage of radioactive water, it’s very important to meet the strict requirements of assembling and sealing the can for the safe use of the pump. The material of the can is Hastelloy C-276while the material of the stator and rotor end is316L. To achieve excellent weld, the process of laser dissimilar welding is researched in both chemical composition and weld formation improvement aspects. The morphorology, microstructure, elements distribution, phase and corrosion resistance property of the dissimilar weld of Hastelloy C-276and316L is analysed by optical microscope, EPMA, EDS, XRD and electrochemical corrosion method.The work is mainly consisted of the follow parts:(1) The0.5mm Hastelloy C-276alloy and316L stainless steel are welded by using the JK701H type Nd:YAG pulsed laser and proper welding parameters. The pulse duration, single pulse energy, pulse frequency, welding speed, defocus distance and energy distribution are chosen as parameters of pulse laser welding which are researched by analyzing the welding morphology due to the welding parameters and are optimized;(2) With the optical microscope of Olympus MX40, the mic rcstructures of different sections of the dissimilare weld of Hastelloy C-276alloy and316L stainless steel are observed. The characteristics of the microstructure welded by pulse laser are summarized. The effect of the change of the welding paramaeters on microstructure of the dissimilar weld is researched. Based on the theory of solidification, the change of the microstructure is analysed;(3) With EPMA (Electron Probe Microanalysis Analyzer) of Shimadzu Epma1600and EDS (Energy Dispersive Spectrometer) of the SUPRA55SAPPHIRE, the element distribution is analysed. Based on the element distribution datas and the Creq/Nieq theory, the possibility of contain of hard brittle phase δ ferrite in the weld is analysed.(4) With the XRD (X Ray Diffraction) of Panalytical Empyrean, the dissimilare weld of Hastelloy C-276alloy and316L stainless steel are detected. The phase of the weld is analysed based on datas of the dissimilar weld;(5) With the electrochemical mesure equipment of Parstat2273, the polarization curves detected in3%aqueous NaCl solution of Hastelloy C-276alloy,316L stainless steel and three different kinds of dissimilar welds are generalized. Based on the datas, the effect of energy distribution on the corrosion resistance property of the dissimilar weld is analysed.