The Study On Corrosion Resistance Of Laser Cladding Layer Of Ni-Cr-Mo Allcy

The high salt content in the seawater,especially in the presence of a large number of chlorine salts make it a good electrolyte solution,the corrosion of metal is particularly strong,the conventional metal materials in the ocean corrosion environment is difficult to bear.Stainless steel which has a relatively good corrosion resistance is not very good to meet the requirements of corrosion resistance,while the use of nickel based alloys,the cost will rise a lot.Laser cladding technology is a new surface modification technology,which can be used in the low price of conventional substrate cladding layer has excellent properties of materials,has a good application prospects.Based on the above background,the subject of the use of laser cladding technology in several Ni-Cr-Mo cladding layer formed on the surface of low carbon steel,and the use of electrochemical workstation,scanning electron microscope,X ray diffraction analysis comparing the corrosion resistance of samples of several different components in self-made seawater and stronger corrosion in FeC13 solution.The experimental results are as follows:1)Increasing Cr content in the composition ofHastelloy C22 alloy can increase the open circuit voltage of the cladding layer in seawater,and reduce the corrosion tendency of the material.The experimental results show that the standard Hastelloy C22 in 3.5%NaCl aqueous solution open circuit voltage is-0.511V,the Cr content increased to 26%the open circuit voltage increased to-0.393V,and increased to 28%the open circuit voltage increased to-0.348V.This is because the increase in the surface layer Cr content will enhance the surface passivation stability,passivation ability;2)Increasing the Cr content of the sample laser can reduce the self etching current and enhance the corrosion resistance of the cladding layer.The experiment shows the standard of Hastelloy C22 in simulated seawater corrosion current is 1.137×10-6 A/cm2,will enhance the content of Cr to 26%when the corrosion current was reduced to 3.305×10-7 A/cm2,increased to 28%when the self corrosion current is reduced to 1,93×10-7 A/cm2.Because the increase of Cr content can improve the quality of the surface passivation film,the passive film is thicker,and the self repairing ability can be improved;3)It was found that the pitting potential of the samples changed little,which showed that the corrosion resistance of the materials could not be improved obviously;4)When the mass fraction of Cr reached 30%,the crack appeared on the specimen surface.From the microscopic images show that punctate substance in the coating containing,and increase the punctate substance with Cr content increased,EDS analysis can be more C,Mo dots and W elements,it may be because the Cr elements have promoted the segregation of impurity atoms,C,Mo and W elements and promote the accumulation the WC and MoC phase formation,the hard phase volume with the increase of Cr elements and the corresponding increase,to a certain extent will make the specimen the ductility,prone to defects.