Mechanical And Corrosion Properties Of Hastelloy C-276/316L Laser Dissimilar Welding

Uuclear power, as a clean energy, has the advantages of safety and high efficiency, becoming an inportant green energy and has broad prospects to promote the sustainable development. The state council promulgated "Medium and Long-term Development Plan of Nuclear Power" in2007. The plan calls for that until2020China should master the advanced pressurized water reactor unclear power technology and has the ability of the mass construction of Chinese nuclear power station. So as to achieve this goal, China brought in advanced nuclear power station of new generation--API000(Advanced Passive PWRS) in the way of comprehensive technology transfer from America.Using the canned motor, the sealing of shield and end cover in AP1000is not only the basis of the normal work of the nuclear main pump, but also the emphases and difficulties in the process of designning and manufacturing. Hastelloy C-276(C-276) is a super Nickel alloy and316L is stainless steel of austenite. Because of both of them having the outstanding mechanical property and corrosion resistance performance, they are used for the shield and end cover in the nuclear main pump. To achivee the basic requirements of the nuclear main pump, this paper uses continuous laser welding technology. On the basis of obtaining good weld morphology, using the tensile and hardness experiment, this article test mechanical properties of weld. And chemical and electrochemical corrosion methods are adopted to compare the differences of corrosion resistance between base material and weld. Meanwhile a process method to ameliorate the corrosion performance of weld is also putted forward. The following is the main content of this paper:(1) To optimizate the process parameters. Through univariate tests, the parameters of continuous laser are studied:the influence of the laser power, speed of welding, laser defocusing amout and laser offset on welding C-276/316L sheet are studied and finally get the optimal welding parameters.(2) Mechanical property research of weld. Using the tensile test, the heterogeneous weld’s mechanical properties are studied, doing the comparation to the parent metal. By using the scanning electron microscope(SEM), the weld microstruture is viewed. Hardness differences between weld and parent materials are studied. (3) Corrosion resistance resesrch of weld. The differences C-276,316L and weld corrosion in strong acid are analyzed. By the means of electrochemical corrosion experiments, electrochemical polarization curve in different solution is tested. With the help of SEM the corrosion type is analyzed, and with the help of X-ray spectrometer (EDS) the elements in the weld is tested. From the aspect of element otherness, the causees of the discrepancy among the three is explainned.(4) Influence of the laser offset to corrosion performance of weld. Adjusting the position of the laser relativelly to joint weld. Under different offsets, its polarization curve and electrochemical impedance in HCL solution is tested. Corrosion voltage, density of corrosion current and resistance of charge transfer are used to analyse the property difference. Testting weld element content under different offsets by means of EDS and explain the corrosive differences.