Nickel-Based Self-Fluxing Alloy Coating Material And Its Corrosion Resistance Research

Corrosion is one of the main failure modes of mechanical parts,and the annual economic losses caused by corrosion problems are increasing year by year.The surface cladding process is an important means for metal component manufacturers to resist corrosion hazards.This research is based on the ball valve widely used in petroleum and coal chemical enterprises.The corrosion resistance of nickel-based self-fluxing coating materials used in ball valve spools in acidic environment is the research goal.Nickel-based self-fluxing alloy samples were prepared by high-frequency induction cladding process.The polarization curves of the samples obtained by electrochemical workstation test in corrosive media were the main basis for judging the corrosion resistance of the coating.The effects of nickel-based self-fluxing alloy composition on the hardness and melting point of the alloy were studied by software simulation and test data analysis.15 kinds of nickel-based self-fluxing alloy powder samples and 4 kinds of typical nickel-based corrosion-resistant alloys were tested by comparison.The characteristics of the polarization curves of nickel-based self-fluxing alloy samples prepared in acidic solution,and the nickel-based self-fluxing alloy powder were analyzed with reference to software simulation results,XRD diffraction patterns and microstructure pictures.The influence of factors such as element composition,test ambient temperature and sample cooling rate on the corrosion resistance of the sample.By analyzing the nickel-based self-fluxing alloy powder composition and related physical property data and using software simulation analysis,it is known that the content of C,B and Cr directly affects the hardness of the alloy,and its content is related to the precipitation of the hard phase in the alloy.The B element plays a major role in lowering the melting point of the alloy in the alloy,while the important metal elements that the Si element can protect are not lost.Test samples were prepared using high frequency induction cladding equipment and vacuum melting furnace equipment,and 15 kinds of nickel-based self-fluxing alloy samples,4 kinds of nickel-based corrosion-resistant alloy samples,and 12 kinds of nickel-based design components were tested.Corrosion resistance of self-fluxing alloy powder samples,comparative analysis of test results.The experiment found that reducing the content of C and B in the alloy powder,increasing the content of Cr and adding elements such as Cu,Mo and rare earth can improve the corrosion resistance of the alloy to some extent.B has a great damage to the corrosion resistance of the alloy,and a small addition of Si element will improve the corrosion resistance of the alloy.When the addition amount is 2%,its corrosion resistance in 0.5mol/L HNO3 solution is about 63%of Ni60A.The addition of Cu can significantly increase the corrosion potential of the alloy and reduce the corrosion tendency of the alloy in a nitric acid solution.Among them,when the addition amount of Cu powder is 1%,the corrosion resistance of the sample is optimal,and the corrosion current density is reduced by about 72.9%compared with the Ni60A sample.The addition of Mo element can further improve the corrosion resistance of the alloy.The ambient temperature has a great influence on the corrosion resistance of the alloy.The experiments were carried out with Ni55A,Ni60A and Ni60C.When the ambient temperature was 25?,45? and 60 ?,the corrosion current density of each sample in 0.lmol/L H2SO4 solution accelerated with the increase of ambient temperature.The elemental composition of each sample is different,and the corrosion resistance is affected by the temperature of the corrosive medium.Among them,Ni60C sample has the effect of increasing the corrosion resistance of the coating due to the addition of Cu and Mo elements.When the sample is prepared,the cooling rate also has an effect on the corrosion resistance of the alloy.Taking Ni60C as the research object,the faster the sample cooling rate,the smaller the crystal grains formed in the alloy,the more the number of grain boundaries,and the more diffusion channels of Cr and Mo elements in the alloy,resulting in the coating at 0.5mol/L.The corrosion resistance in the HNO3 solution is also enhanced.When the sample is cooled at a rate of 500?/s,the corrosion rate in the corrosion solution is only 57%of the sample cooled at 25?/s.