Research On Wear Resistance And Corrosion Resistance Of Fe-based Alloy Coating Deposited By Ultra-high-speed Laser Cladding

Hydraulic support was the main supporting equipment during the coal mining process.Due to the poor work environment under the mine,surface corrosion and wear were easy to occur,resulting in seal failure,and creating the potential for security problems.So that,surface strengthening treatment should be applied to the hydraulic support.The chromium electroplating(EP)was widely used in industry,but toxic Cr⁶⁺was easily produced during this process,causing environmental damage and contrary to the protection and sustainable development policy of green environment.Therefore,highly efficient wear-resistant and corrosion-resistant coating preparation technology for the hydraulic support was urgently needed.The ultra-high-speed laser cladding technology(UHSLC)was proposed in 2017,which had an increased cladding efficiency of 10?50times to conventional laser cladding(CLC)technology,greatly reduced thermal effect to the substrate,good surface finish coating,and become a potential technology to replace EP,since it was a technology of green,lower cost and automation.Fe-based alloy wear-resistant and corrosion-resistant coating was deposited using CLC and UHSLC process on the substrate of 27Si Mn steel in this research,respectively.The surface morphology,microstructure,and hardness of the coating prepared by different process was analyzed,and the results showed that compared with the CLC coating,the UHSLC coating had smoother surface,lower dilution ratio of about 2%,and decreased heat-affected zone of only 55?m.At the same time,under extremely high cooling rate,the dendritic structure of the UHSLC coating was finer,the elements distributed was more uniformly.Both the CLC and the UHSLC coating were composed of martensite,ferrite,and carbides,while the martensite and carbides in the UHSLC coating was less,making the UHSLC coating had a lower hardness.The friction and wear behaviors of UHSLC coating,CLC coating and EP coating were comparatively studied,and the abrasion mechanisms were analyzed.The results showed due to the more content of martensite and carbides,the friction coefficient and wear volume of CLC coating was lower under the same experimental conditions,which meant CLC coating had better wear resistance.At the same time,the wear resistance of the UHSLC coating was more than 3times of the EP coating.And the primary wear mechanism was adhesive wear for EP coating,while abrasive wear for UHSLC coating.The electrochemical tests were conducted,and the evolution of corrosion products and microstructure of CLC and UHSLC coating during the 480h neutral salt spray corrosion test were analyzed.The results illustrated UHSLC coating had better corrosion resistance,since its corrosion potential increased from-5.6V to-5.1V;the corrosion current density decreased from 1.3×10^-5A/cm²to 1.5×10^-7A/cm²compared to CLC coating.At the initial corrosion stage,the corrosion degree of UHSLC coating was light.After 144h,obviously continuously distributed oxidation products were formed and concentrated,the corrosion time was longer,the development of the corrosion products and its morphology was slower.After 480h,the corrosion rates of the above two coatings both gradually stabilized at 0.15g/(m²·h).The corrosion products were mainly Fe oxides,and the corrosion mechanism was electrochemical corrosion caused by the uneven surface structure of the coating.