| Because of its excellent structural strength,fracture toughness and high cycle fatigue properties,special steel is widely used in the manufacture of aircraft landing gear,submarine oil pipeline and pressure vessel valve in the fields of transportation,petrochemical industry and oil and gas storage and transportation.Under actual working conditions,the effects of load impact and corrosive media often place these parts in extremely harsh actual working conditions.Once these parts and components fail,they will pose an extremely serious threat to the safety of people’s production and life,and pose a serious safety hazard.Therefore,it is particularly important to improve its corrosion resistance.Laser cladding technology has been widely used in recent years and has gradually become a research hotspot due to its high power density,high self-cooling speed of the substrate,small local deformation and high operation accuracy.In response to the above problems,this subject aims to develop a new type of corrosion-resistant coating.Firstly,the corrosion process and mechanism of 300 M steel substrate in neutral salt spray environment are explored,and it is found that Cr element is a favorable factor to improve its corrosion resistance.Subsequently,laser cladding technology was used to prepare 316 L stainless steel and Hastelloy C-276corrosion-resistant coatings with different Cr element contents on the surface of the substrate with varying process parameters.The focus is on the corrosion process and mechanism of 300 M steel in a neutral salt spray environment,the influence of process parameters on the structure and performance of laser cladding corrosion-resistant coatings,and the comparison of the comprehensive performance of two different corrosion-resistant coatings.In this paper,firstly,by means of optical microscope,scanning electron microscope and energy spectrometer,X-ray diffractometer,three-dimensional profiler and electrochemical workstation,the weightlessness method,electrochemical test method and other research methods are used to analyze the 300 M under neutral salt spray atmosphere.The corrosion process and products of the steel substrate were analyzed and characterized,and its corrosion mechanism was discussed,in preparation for the next step of preparing the corrosion-resistant coating on its surface;Secondly,a set of reasonable parameters was selected on the basis of the preliminary experiment,and the prefabricated powder method and the synchronous powder feeding method were respectively applied on the surface of 300 M steel using laser cladding technology,and 316 L stainless steel powder and C-276 alloy powder were used as cladding materials.Two kinds of corrosion-resistant coatings were prepared with variable power.Through the above methods and methods,the macro morphology,phase structure,metallographic structure,element distribution,hardness and corrosion resistance of the cladding layer were characterized and analyzed,and the influence of laser power on the structure and mechanics of the cladding layer was discussed.And the influence law of corrosion resistance;Finally,based on the previous work,the comprehensive performance of the two laser cladding coatings is compared.The experimental results show that: 300 M steel exhibits poor corrosion resistance in a salt spray environment.The two corrosion-resistant coatings prepared by laser cladding technology can achieve the purpose of improving the corrosion resistance of 300 M steel.The influence law of laser power on the organization structure of the two is basically the same.Although the Cr element contributes significantly to the improvement of the corrosion resistance of 300 M steel and the C-276 coating is weaker than the 316 L stainless steel coating in terms of hardness,from the perspective of cladding quality and corrosion resistance,the former is significantly better than the latter.The self-corrosion current density is 24 times lower than that of the 300 M steel substrate,which significantly improves its corrosion resistance. |
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