Preparation And Corrosion Resistance Analysis Of Nitrogen Containing Nickel Based Flux Cored Wire

Because of its good corrosion resistance,the research and development of nickel based alloys have attracted great attention of scholars at home and abroad.However,due to the high price of nickel and the relative lack of nickel resources in China,a large number of nickel needs to be imported from abroad,which seriously limits the development of China's industry.Therefore,it is imperative to develop a low nickel alloy.Because N and Ni are both austenite elements,part of nitrogen can be used to replace nickel base to reduce Ni content;In addition,N in austenite matrix can also improve the strength,fatigue resistance and corrosion resistance.Therefore,in this paper,according to Inconel 625 flux cored wire,a certain amount of N is added to the nickel based flux cored wire to replace Ni,so as to realize high N and low Ni,,and the high temperature static immersion corrosion properties of chloride molten salt and sulfate under 700?and 900?of the Ni based deposited metal obtained under the optimal formula are tested.At the same time,the corrosion resistance and corrosion mechanism of high N and low Ni deposited metal were investigated by comparing with the existing Inconel 625 deposited metal.The conclusions are as follows:(1)Compared with the existing Inconel 625 flux cored wire,a kind of nitrogen-containing nickel based flux cored wire was obtained by orthogonal test with four factors and four levels.The optimal formula was 42.0%Ni,26.0%Cr,0.21%N and 2.6%W.The Ni based deposited metal with nitrogen obtained by surfacing has excellent corrosion resistance,which is equivalent to that of Inconel 625.The addition of N can reduce the dilution of Cr,consume H⁺,and change the local corrosion environment.(2)For the corrosion resistance of chloride molten salt,the corrosion resistance of Ni based deposited metal with nitrogen at 700?and 900?is better than Inconel 625.In addition,the synergistic effect of N and Monot only reduces the effect of p H value,but also makes MoO₄^2-is stable and helps to form ammonia.At the same time,it can prevent Cl^-and H⁺from entering,which is beneficial to form Cr₂O₃ protective film and improve its corrosion resistance.(3)For so resistance SO₄^2-in molten salt,the corrosion resistance of Ni based deposited metal with nitrogen at 700?and 900?is better than Inconel 625.The presence of N element improves the hot corrosion resistance of S,and relatively high concentration of Cr element provides better protection against corrosion of corrosion salt.In the process of thermal corrosion,N on the N-element enrichment interface of oxide metal interface can form stable compound nitride layer,and inhibit SO₄^2-enters,and promotes the formation of Cr₂O₃ protective layer on the deposited metal surface;compared with Inconel 625 deposited metal,internal oxides and sulfides are formed in the Cr depletion region,and the S element invades into Inconel 625 deposited metal more,which leads to the decrease of its corrosion resistance.