| Cladding coatings preparation by laser and plasma cladding have been widely used becsuse it can effectively improve the physical and chemical properties of materials surface,then the wear resistance of materials can be improved.Cr3C2/TiC composite coatings are a promising structural material in high temperature,corrosive and abrasive environments.In this work,Ni-base Cr3C2/TiC composite coating was used to prepare on Q235 steel by plasma and laser cladding process using NiCr-Cr3C2,Ti,Ni,Cr,graphite and Ni55 powder mixture as precursor.The phase,microstructures,microhardness,wear resistance of the coatings were analyzed and also study the ceramic phase content of composite coating affecting on microstructure and properties of coating.The mian research results are as followed:Composite coatings successfully prepared on the substrate by plasma cladding and laser cladding techniques.The carbide in the the plasma cladding mainly consisted of Cr7C3 and other main phases included Cr3C2,Cr23C6,Cr5B3 and Ni3Si.In-situ synthesis by laser cladding to prepare the main phase of Cr7C3,other Cr3C2,?-[Ni,Cr]and the plasma cladding Cr3C2 added with Ti powder is mainly Cr23C6,Cr7C3,CrB,TiC The composite coating of the strengthened phase.The amount of carbides in coatings increase with the increase of the mass fractions of ceramic phase powders in the mixed powders.When the content of the original cladding powder NiCr-Cr3C2 is low,Cr7C3 accumulates in the vicinity of the Cr23C6 phase because the Cr7C3 is limited by the growth advantage of Cr23C6,so,the size is small.With the increases content of Cr and C in the molten pool,the Cr23C6 gradually changes to Cr7C3 in a small temperature range during the cooling process.On this basis,Ti powder was added,and then Cr3C2/TiC composite coating have been successfully preparing.With lower Ti powder,the chromium carbide phase was radially distributed in the vicinity of TiC particles,with the increase of Ti content,NiCr-Cr3C2 and Ti powders react more fully,and the carbide phase of chromium mainly exists in Cr7C3 type,the microstructure of ceramic phase is refined,and the distribution of TiC particles is more uniform.The composite coating with the main reinforcing phase of Cr7C3 was prepared on the surface of Q23 5 steel by laser cladding in-situ synthesis,the coating is mainly dendritic,and the coating structure is gradually refined as the original cladding powder is added.As the content of the ceramic phase increases,the microhardness of the coating increases.The maximum average microhardness preperd by plasma cladding is 7 times to substrate,and the highest average hardness of laser cladding can reach 1093HV,which is about 6 times,for the Cr3C2/TiC composite coating,the Cr3C2 particles partially melts and reacts with Ti to synthesize the TiC particles,which reduces the hardness of the coating,so the maximum average hardness is about 5 times to Q235.The ceramic phase not only acts to hinder the movement of dislocations,but also makes the coating have a higher hardness and improves the plastic toughness of the materialThe wear results of the plasma cladding Cr3C2 composite coatings under the same load force show that the average friction coefficient(COF)of the coating decreases with the increase of the ceramic phase content,and the wear volume loss decreases,the wear surface is flat,and the number of furrows is shallow,with the increase of load force,the COF of the same coating is gradually decreased,and the wear volume is increasing,at 50%content,cracks appear on the wear surface of the coating.The COF of Cr3C2/TiC composite coatings are much lower than that of the matrix under different wear conditions,the wear resistance is significantly improved,and the wear loss is minimum at 1.0Hz.The COF of the coating with different Cr/C content of the laser cladding coating are stable and much lower than Q235,and due to the influence of the compacted layer structure formed during the wear process,A3 has a lower friction coefficient and the wear process is relatively stable. |
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