Preparation Of High Cr Content Ni-Based Alloy Wire And Its High Temperature Oxidation And Corrosion Resistance

During the running of equipments such as boiler in power plants,high temperature oxidation and hot corrosion will be easily generated to their components and parts.As to this problem,a nickel-based alloy wire with high Cr content is developed in this paper.When it is sprayed on the surface of ordinary steels,the effective protection can be achieved on engineering components,and the production cost can also be greatly reduced.By means of vacuum induction melting,a nickel-based alloy with high Cr content?42.98%Cr?is been successfully prepared by reasonable design of alloy composition and optimization of smelting process.The further forging and drawing are conducted to as-cast alloy,and the welding wire with a diameter of 2mm is finally obtained.Microstructure and mechanical properties are investigated on the prepared alloy ingots both in as-cast and forged state,and welding wire respectively.Moreover,X-ray diffraction analysis and tensile fracture scanning observation are carried out to alloy ingots both in as-cast and forged state.Results show that microstructure and mechanical properties of as-cast alloy in line with expectations,the mechanical properties of welding wire can meet the requirements in paractical application.In order to further explore the high temperature resistance and hot corrosion resistance of nickel-based alloy welding wire with high Cr content,the Q345 steel and 304 stainless steel are selected as substrates respectively,which are often used as boiler pipeline and heating surface materials at high temperature.The Ni-based alloy coatings with high Cr content are prepared on substrate surfaces by using arc spraying process.The oxidation and hot corrosion behaviors are investigated respectively for Q345 steel coating under 750?and 304 stainless steel under 1000?.As a contrast,the high temperature oxidation and hot corrosion behavior of Q345 steel and 304stainless steel without coating are also investigated under the same experimental condition.Results show that,coatings are sprayed on the two different substrates,after high temperature oxidation and hot corrosion from 0-60 hours,the oxidation kinetics curves and corrosion kinetics curves of coated specimens present parabolic pattern,whose fitting degree is higher than 0.97.While the oxidation kinetic curves and corrosion kinetic curves of substrates?without coating?tend to increase linearly.Microstructure analyses indicate that,a continuous Cr₂O₃ and NiCr₂O₄ oxides with spinel structure generate on coating surfaces at high temperature,these constituent phases are compact,and distribute uniformly in coatings,which can effectively prevent oxygen from penetrating into the matrix,thus the continuous oxidation and corrosion can be inhibited.On the whole,the nickel-based alloy coatings with high Cr content are prepared on the surface of Q345 steel and 304 stainless steel respectively by using arc spraying,and good oxidation resistance and hot corrosion resistance can be achieved at high temperature.It can effectively improve the service temperature and working life of steel components and parts in power plants.