Study On Microstructure,friction And Wear Characteristics Of NbC/MoS₂/CeO₂/Ni Matrix Composite Coatings By Laser Cladding

Laser cladding is a new high-energy surface modification technology,mainly used in the field of aviation,automotive and biomedical.And now this technology also has great potential applications in the mold industry.H13 steel is one kind of common mold steel,its surface structure can be improved by laser cladding,which lead to a longer life.In this paper,nickel-based self-fluxing alloy coating,NbC+nickel-based,NbC+MoS₂+nickel-based,NbC+MoS₂+CeO₂+nickel-based composite coating were prepared on the surface of H13 steel by laser cladding method,then the ingredients are optimized.XRD,SEM and EDS were used to study the microstructure and properties of the coating.The microhardness was tested and the friction and wear properties were tested under the conditions of pressure 100N,speed 100 r/min and time 7200 s at room temperature and medium temperature 400?.The results show as follows:The NbC/Ni60 cladding layer is composed of?-Ni solid solution,Cr₂₃C₆ and NbC among these composition.NbC and carbide Cr₂₃C₆ worked as hard enhanced phase.The cladding layer is dominated by columnar crystals and mesons,and NbC can be used to refine the grain size.The microhardness of the cladding layer is about 2 to 3 times that of the substrate.The microhardness of cladding increases with the increase of NbC content,and the microhardness of subside is even higher than that of surface layer.NbC/Ni60 composite coating has good friction and wear characteristics.The friction and friction coefficient of NbC/Ni60 cladding layer are higher than that of H13 heat treatment sample at room temperature.In addition,NbC/Ni60 cladding layer wear is also significantly lower than H13 steel.When the content of NbC is 20%,the wear amount reaches the minimum value.When the NbC content is low,the wear mechanism of cladding layer is dominated by typical adhesive wear.With the increase of NbC content,the wear mechanism of cladding layer gradually changed to abrasive wear.Under medium temperature conditions,the wear amount of 20%NbC cladding layer is the smallest.The friction coefficient and friction coefficient of 20%NbC cladding layer are maximum at medium temperature.The wear mechanism of H13 steel samples is mainly oxidation wear and adhesive wear.The wear mechanism of the steel with NbC is mainly abrasive wear and adhesive wear.The phase composition of MoS₂/20%NbC/Ni60 cladding layer is similar to that of NbC/Ni60 cladding layer.When the MoS₂ content is 2.5%and 5%,the Fe-Cr phase is formed.With the increase of MoS₂ content,Fe-Cr phase disappeared.After adding MoS₂,the microhardness of the cladding layer is significantly reduced,and the presence of the crack has a detrimental effect.At the same time,Fe-Cr phase can enhance the surface microhardness value.Due to the two-combined effect,the cladding layer containing 5%MoS₂ reaches the highest hardness.The addition of MoS₂ has important influence on the friction and wear characteristics of the composite coating.The friction and friction coefficient of the cladding layer are reduced and the wear amount is increased at room temperature.5%MoS₂ lead to the best wear resistance.The wear mechanism of 2.5%MoS₂ cladding layer is mainly due to adhesive wear.With the increase of MoS₂ content,the wear mechanism of cladding layer was mainly abrasive wear.At medium temperature,the wear loss of 5%MoS₂ cladding layer is the minimum,0.008g.The friction coefficient and friction coefficient can be effectively reduced by adding MoS₂.At the same time,the friction and friction coefficient of cladding layer increase gradually with the increase of MoS₂ content.After friction and wear,the surface cracks of the cladding layer disappeared,and the surface of 2.5%MoS₂ and 5%MoS₂ cladding layer was smoother.CeO₂/5%MoS₂/20%NbC/Ni60 cladding layer with Ce₂O₂S phase has little surface defects and promotes grain refinement.CeO₂ addition,clad layer decreased microhardness.The addition of CeO₂ can improve the friction and wear characteristics of the coating.The frictional force and the friction coefficient of the cladding layer are similar,and the wear mechanism is changed from abrasive wear to adhesive wear and fatigue wear.The wear amount decreases with the increase of CeO₂ content,and the wear amount of 3%Ce O₂ cladding layer is the smallest,which is 0.003g.At medium temperature,the wear rate decreased gradually with the increase of CeO₂ content and the minimum value was 0.003g.The friction and friction coefficient of the cladding layer are similar to that of the cladding layer.However,the friction and friction coefficient of CeO₂ cladding layer is unstable and the fluctuation is smaller.The friction and friction coefficient of Ce O₂ cladding layer is unstable and the range of fluctuation is large.The main wear mechanisms of CeO₂ are adhesion wear and oxidation wear.