TiC Modified Ni-based Composite Coatings Based On Induction Cladding

Die often works in high temperature,high pressure,corrosion and other special environments.Therefore,wear,corrosion and fatigue failure are important factors affecting die life.Because failure occurs mostly on the surface of dies,surface engineering technology is often used to improve the surface properties of dies and prolong the service life of dies.The use of high-frequency induction cladding technology to prepare particle-reinforced Ni-based composite coatings on the die surface has the advantages of high heating efficiency,less pollution,and low cost.At present,the cermet coating prepared by induction cladding technology generally uses WC and Cr₃C₂ with good Ni infiltration and low resistivity as the reinforcement phase,while TiC is rarely used as the reinforcement phase.TiC as an ideal ceramic reinforcement has excellent mechanical properties and chemical properties,but there are still some technical difficulties in the preparation of TiC-reinforced Ni-based alloys by induction cladding,such as poor wettability between TiC particles and Ni-based alloys and low induction heating efficiency because of high resistivity of TiC ceramic particles.Therefore,the study of electroless Ni-coated TiC particles to improve the poor wettability and high resistivity problems,as well as to improve the surface properties of the metal matrix composite coatings reinforced by ceramic particles,has important practical value and exploration significance.In this paper,Ni-coated TiC particles were prepared by electroless plating,and pure Ni60 and Ni-coated TiC+Ni60 coatings were prepared on the surface of H13 steel using induction cladding technology.The phase and microstructure of the coating were analyzed by X-ray diffractometry,field emission scanning electron microscopy,and energy dispersive spectroscopy.The surface hardness of the coating was measured using a microhardness tester.The anti-aluminum,anti-copper corrosion and thermal fatigue resistances of the coatings were analyzed by an immersion test and a thermal fatigue test.The results show:?1?The surface of TiC was coated with a complete and dense Ni-P alloy coating by electroless plating.The thickness of the coating is 1.2 ?m.The wettability between the coated TiC and the Ni-based alloy in the coating is improved,and the resistance rate of the TiC particles is reduced,which effectively improves the efficiency of coating during induction heating.?2?The best cladding process is: using sodium silicate solution as a binder,coating thickness 1.0mm,preheating at 200 A for 20 s,heating at 800 A for 15 s,and air cooling after heating.?3?The pure Ni60 coating is mainly composed of ?-?Fe,Ni?,Cr₇C₃,Ni₃ Si,Cr B.There are some pin-like and massive structures distributed in the coating.The TiC+Ni60 coating is worse because of high resistivity and insufficient heating resulting from TiC addition.The Ni-coated TiC+Ni60 coating is mainly composed of ?-?Fe,Ni?,Cr23C6,Ni3 Si and TiC.The coating is mainly composed of a dense eutectic structure and a hardened reinforcing phase.The surface hardness of Ni60 coating and Ni-coated TiC+Ni60 coating are 839.6HV and 982.90 HV,respectively,which are much higher than that of H₁₃ steel substrate367.08 HV.?4?After 1h aluminum liquid erosion test,both Ni60 coating and Ni-coated TiC+Ni60 coating exhibited excellent resistance to molten aluminum corrosion,the substrate well isolated from the direct contact of the molten aluminum and the coatin g,and improved the corrosion resistance of the H₁₃ steel substrate.After 1h copper corrosion test,the Ni-coated TiC+Ni60 coating has excellent copper corrosion resistance,and the corrosion area is 20?m thick;the Ni60 coating and the H₁₃ steel substrate have pits and corrosion on the surface of the copper solution.The area is 50?m thick.?5?After being subjected to 900 thermal shock cycles,the matrix H₁₃,Ni60 coatings,and Ni-coated TiC+Ni60 coatings all exhibited a certain degree of thermal fatigue failure.The thermal fatigue of H₁₃ steel matrix is in the form of sheet surface failure.The thermal fatigue of Ni60 coating is the crack initiation and growth under the action of surface stress.The thermal fatigue of Ni-coated TiC+Ni60 coating is the second failure mode.The stress concentration in the phase-inclusion TiC causes crack initiation and growth.