Applied Research About Thermal Resistant Layer Of Laser Cladding Cr₃C₂ On The Chamber Surface Of Hot Forging Die

The normal Failure Forms of forging the hot forging die of steel forgings are main thermal fatigue wear and plastic deformation, the place of failure is on the Chamber surface and near Surface Layer. The long time practice has proved, at present, the homogenized hot working die steel is hard to fulfill the application performance of hot forging die chamber surface and near surface layer. The life problem coming from it has not made any developments.Mitigating thermal stress grads material and surface engineering technology have provided some new idea and new method for solving the using life of hot forging die. The team of author's is studying the problem. This paper is trying to prepare the cermet heat resistant wear resistant layer on the chamber surface of hot forging die in laser cladding technology, it's a exploratory experiment research of solving the chamber surface strengthen problem of the hot forging die.The first part of this paper summarizes the research of hot forging die in the world, mainly introduces the Failure Forms of hot forging die, the infection of the theremal stress to the life of hot forging die. Then,introduces briefly the development of surface engineering technology, giving some technology of surface cladding technology. Next introduces the development of laser cladding, and its theory and process method.The second part of this paper is designing an experiment of laser cladding. The Substrate material is W₆Mo₅Cr₄V₂ which is one of the chamber near surface layer of hot forging die gradient material structure. The experience take a macro-analyses and micro-analyses of the different laser processing parameters, including the analyses of Metallographic, the analyses of XRD, the analyses of EDX, and the analyses of hardness, and select out the reasonable material proportion and laser processing parameters. And the experience still analyses the Ni/Ni-Cr-Cr₃C₂ laser strengthen mechanism, the reflection of different laser processing parameters to the hardness and microsturcture of the cladding. The experience also measures the theremal stress Parameters which includes elastic module E, linear expansibility a,thermal coefficientλand specific heat c.The third part analysed the measuring result, and obtain some conclusion.The microstructure analyses show three regions with different microstructure exist in the There surface of layer of clad samples: that the cladding layer, heat influence and combined zone. There is plane crystal zone between cladding layer and heat influence, after being corroded and we can see the plane crystal is made ofγ-Ni plane crystal. There is bunchiness Eutectic under the cladding layer, there is lots of black block and columniation crystal structure, in the middle part of the cladding layer. There is also a lot of hoar strip and block crystal in the whole cladding zone.Phase analysis and hardness analysis show, the phase of cladding layer is mainly made by Y-Ni, Cr₇C₃,Cr₃C₂,Cr²³C₆,CrB,M₂₃(C,B)₆,γ- (Ni, Fe) , at the same time, the cladding layer's microhardness is enhanced.Physical function parameters analysis shows, the linear expansibility of cladding layer is influenced obviously under 200℃, but above 200℃, the linear expansibility's raising curve is slowed down, and the linear expansibility of cladding layer is higher than theoretic value. The thermal coefficient and specific heat is lower than the theoretic value, the elastic module's value is higher than substrate steel.The results shows that the laser cladding process has a lot of effect to the macro appearance of cladding layer ,to the microstructure and to the performance of the cladding layer. The results prove that using the laser power P=1.7Kw, scanning velocity V=4mm/s, spot diameter D=3mm, cladding thickness T=0.6mm, 50%: 50% Ni60:Ni-Cr-Cr₃C₂ as laser cladding process can obtain the laser coating with lubricous tight surface, tiny dilution rate ,fining microstructure and higher micro hardness and fine metallurgical-bonding Interface. The result proves this is a prospect methord for improving the live of hot forging die.