Research On Wear And Corrosion Resistance Of Laser-clad Zr-Al-Co(Ti) Amorphous-nanocrystalline Coating

Amorphous alloys have attracted much attention due to their excellent properties such as high strength,hardness,wear and corrosion resistance.However,the poor glass forming ability hinders the application of such alloys in bulk structural members.The preparation of amorphous nanocrystalline coatings with excellent wear and corrosion resistance has become an optional scheme.In the work,Zr60-xAl15Co25Tix(x=0,5,10,15 at%)amorphous nanocrystalline coatings were prepared by laser cladding technique with amorphous strips as cladding materials.The effects of Ti on the structure,hardness,corrosion and wear resistance of the coatings were characterized by X-ray diffraction(XRD),optical microscopy(OM),scanning electron microscopy(SEM),Vickers hardness test machine,electrochemical workstation,three-dimensional topography,and friction and wear tester.Based on this,the effect of concentrations and temperatures of the electrolyte on the corrosion resistance of Zr55Al15CO25Ti5 amorphous nanocrystalline coatings in sulfuric acid solutions were investigated.Finally,the phase constitution,hardness and wear resistance of Zr60-xAl15CO25Tix(x=0,5,10,15 at%)amorphous-nanocrystalline coatings were characterised.The main results are as follows:(1)The coatings were prepared on the Q 235 substrate by laser cladding technique using Zr60-xAl15Co25Tix(x=0,5,10,15 at%)amorphous ribbons as the precursor material.The results show that the hardness of the coating is greatly improved and the corrosion resistance enhanced compared with the matrix.The microhardness of the coating increases with increasing Ti content due to the formation of ZrO2 content in the coating.The corrosion potential and corrosion current density indicate that the Zr55Al15CO25Ti5 coating exhibits relatively high corrosion resistance in 3.5 wt%NaCl solution.(2)The corrosion resistance of Zr55Al15Co25Ti5 amorphous nanocrystalline coatings in sulfuric acid solutions was also investigated at different concentration and temperature.The Zr55Al15CO25Ti5 coating exhibits better corrosion resistance in a sulfuric acid solution at 60?.In the 2%sulfuric acid solution at 70?,pitting corrosion is the main corrosion mode,and the appearance of the passivation film is beneficial to the improvement of corrosion resistance.In the 2%sulfuric acid solution at room temperature,the most positive corrosion potential with the lowest corrosion current density indicates the best corrosion resistance of the coating in this environment.(3)Zr-Al-Co(Ti)amorphous nanocrystalline coatings with various thickness were prepared.XRD results show that the coating consists mainly of ZrO2,Fe and amorphous phases.The laser cladding Zr-based coating can increase the surfacial hardness of the material.The hardness of the coating increases with the increasing of Ti content.The hardness value is the highest when the Ti content is 15 at%,which is due to the highest ZrO2 content.The wear resistance of the coating is also greatly improved compared to the substrate.As the Ti content increases,the wear resistance of the coating increases.The coating containing Ti=15 at%in the system has the best wear resistance.