Study On The Microstructure And Erosion Wear Properties Of Laser Cladding Ni-WC Composite Coating

In recent years,the technology of preparing Ni based alloy WC composite coating on metal surface by laser cladding has attracted wide attention.The coating high performance can be prepared by means of the effective combination of high toughness of Ni based alloy and high wear resistance of WC reinforced particles.Among them,the added amount,shape and distribution of WC particles have a great influence on the performance of the coating.There are a lot of studies on the microstructure,mechanical properties,corrosion resistance and wear resistance of Ni-WC composite coating in the existing literature,but there are few reports on the liquid-solid two-phase flow erosion wear properties and their interaction of Ni-WC composite coating.At present work,Ni45 coating and Ni45-WC composite coatings were prepared on the Q345 steel surfaces laser by laser cladding.The addition content of WC were selected as 10%,20%,30%,40%,50%and 60%respectively.The effect of different WC contents on microstructure and hardness of the nickel-based cladding layers was analysed.The influence of WC content on the corrosion resistance,erosion wear performance and interaction of the cladding layers were investigate by using electrochemical workstation and the erosion wear tester.The morn surface morphologies were observed by scanning electron microscope（SEM）,and the erosion mechanism was analyzed.The results showed as follow:The main phases of the Ni45 cladding layer areγ（Ni,Fe）,Cr₂₃B₆,Fe Ni₃,Ni₃₁Si₁₂,Cr₂B and Ni₃B,etc.After adding WC particles,the amount ofγ（Ni,Fe）phase decreased gradually,the amount of Fe Ni₃and carbide increased gradually,and with the increase of WC content,various forms of carbide and boride appeared,while the undissolved WC phase appeared when the WC content was more than 30%,the types and contents of carbides and boride increased further.The upper part of the Ni45 cladding layer is equiaxed crystals,the middle part is fine dendrites,and the lower part is columnar crystals.After addiing a small amount of WC,the surface dendrite of the cladding layer was refined,the middle of the cladding layer was cellular and a small amount of dendritic,and the bottom of the cladding layer was increased.When the addition of WC was more than 30%,the cladding layer became finer cellular and the undissolved WC particles increased,the surface of the cladding layer is irregular,and the rod-like and long-strip-like eutectic structure gradually forms into the massive and petal-like eutectic structure,and the forming quality of the cladding layer becomes worse.The microhardness of cladding layer increases gradually with the increase of WC content,when WC content is 60%,the microhardness of cladding layer reaches the maximum.The corrosion rate of cladding layer first decreases and then increases with the increase of WC content,when the WC content is 30%,the minimum value appears,and the erosion wear rate of the cladding layer first decreases and then increases with the increase of the WC content.When the WC content is 30%,the erosion wear rate is the lowest,which is 35.71%lower than that of the Ni45 cladding layer and 75.77%lower than that of the substrate,its erosion wear performance is the best.The results for erosion wear tests of the cladding layers show that the pure corrosion effect is greater than the pure erosion effect,but there is a strong interaction between erosion and corrosion.With the increase of WC content,the erosion and wear damage on the surface of the cladding layer shows a trend of first lightening and then increasing.Although the erosion and wear morphology of the Ni45 cladding layer without WC particles was significantly weaker than that of the base material,there were still larger erosion pits,furrows and corrosion marks on the surface;When the WC content increases to 30%,the erosion pits and groove marks on the surface of the cladding layer become the smallest and shallower,the corrosion marks are not obvious,and the coating surface is relatively complete;As the WC content continues to increase,large white hard sediment particles can been found on the surface of the cladding layer,and the massive particles have broken and peeled marks locally,and the erosion pits and groove marks on the gray substrate become larger.When the content of WC is less than 30%,the erosion wear mechanism of ductile materials is dominant,and when the content of WC is 40%and 50%,the composite erosion wear mechanism of ductile-brittle material is shown,and when the content of WC is 60%,the erosion wear mechanism of brittle materials is dominant.