Fabrication And Properties Of Iron-based High-temperature Wear-resistant Laser Cladding Layer

Additive manufacturing has been widely used in industrial field increasingly due to its ability of near-net shape and ability to fabricate complex structural components.As-printed 430 stainless steel has been adopted in high-temperature environments owing to its excellent heat resistance.However,their performance in high-temperature friction environments is not satisfied.Additionally,there are also high requirements for corrosion resistance due to stainless steel is mostly used in complex corrosive environments.Laser cladding technology is widely used to prepare wear-resistant and corrosion resistant coatings due to its advantages in surface repair and re-manufacturing.Therefore,using laser cladding to improve the high-temperature wear resistance and corrosion resistance of 430 stainless steel surface have important significance in application.In this paper,four coatings of Fe-x Cr₇C₃（chromium carbide content 10 wt.%,15 wt.%,20 wt.%,25 wt.%）were prepared on the surface of as-printed 430 stainless steel pieces using laser cladding technology.The effect of Cr₇C₃content on the microstructure of the coating was studied.The effect of friction temperature on the sliding friction properties of the cladding layer was investigated,and the wear mechanism of the cladding layer was revealed.The corrosion performance of the cladding layer in different corrosion solutions（3.5wt.%Na Cl solution,0.5 mol/L HCl solution and 0.5 mol/L H₂SO₄solution）were studied,and the effect of different chromium carbide content on the corrosion resistance of the layers was analyzed.From experimental finding,good metallurgical bonding between the cladding layer and the substrate was observed without cracks at the bonding interface.The cladding layers are consisting ofγ-（Fe,Ni）,Cr,and solid solutions.With the increase of chromium carbide content,large number of elongated or massive carbides appear in the microstructure,resulting in significant refinement of the structure.The maximum surface hardness of the cladding layer is 522.3 HV_0.2,which is2.4 times higher than the average hardness of the 430SS substrate(220.1HV_0.2).Superior high-temperature wear resistant of cladding layer was achieved on the surface of as-printed 430 stainless steel by adding different amounts of Cr₇C₃powder to 253H heat-resistant stainless-steel powder as the material for laser cladding.With the increase of friction temperature,the cladding layer exhibits stronger wear resistance than the substrate.With the increase of chromium carbide content,the wear loss of the cladding layer decreases,indicating that chromium carbide in the cladding layer is conducive to improving high-temperature wear resistance.The wear mechanism of the cladding layer with lower chromium carbide content is mainly adhesive wear.When the chromium carbide content reaches 20 wt.%,the wear mechanism of the cladding layer becomes abrasive wear.The abrasion resistance of the as-printed430 substrate is much higher than that of the cladding layer,and the abrasion resistance of the cladding layer with a chromium carbide content of 20 wt.%is more than three times higher than that of the substrate.Results from the electrochemical polarization and impedance experiments of the sample in three corrosion solutions are indicated.In a0.5 mol/L HCl solution,the capacitive impedance arc of the cladding layer is higher than that of the substrate,indicating that the corrosion resistance of the coating is much better than that of the substrate.In a 0.5mol/L H₂SO₄solution,the corrosion resistance of the substrate is higher than that of the cladding layer,indicating that the addition of chromium carbide is not conducive to the corrosion resistance of the cladding layer in H₂SO₄solution,and the cladding layer is mainly pitting corrosion.In a3.5 wt.%Na Cl solution,the corrosion resistance of the cladding layer is slightly higher than that of the substrate when the chromium carbide content is lower than 20 wt.%.However,the cladding layer with a chromium carbide content of 25 wt.%is prone to form micro batteries due to more micro pores on the surface,which speeds up the corrosion process.Therefore,the corrosion resistance can be lower than that of the substrate.Above all,the corrosion resistance of the cladding layer in a 3.5wt.%Na Cl corrosion solution is better than that of the substrate.