Applied Research About Thermal Resistant Layer Of High Frequency Cladding MoSi₂ On The Chamber Surface Of Hot Forging Die

The main normal Failure Forms of forging the hot forging die made of forging steels are thermal fatigue abrasion and plastic deformation,the failure takes place on the chamber surface and near surface Layer.The long-term practices have proved that recently,the homogenized hot working die steel is hard to meet the performance requirement of hot forging die chamber surface and near surface layer.The life-span problem resulting from it has not yet resolved completely.The technology of grads material relieving thermal stress and surface engineering technology have brought some new ideas and new methods for solving the life-span of hot forging die.This paper is trying to apply high frequency calefaction cladding technique to produce a heat resistant and wear resistant cermet layer on the chamber surface of hot forging die,which is an exploratory experiment research of solving the chamber surface strengthen problem of the hot forging die.The first part of this paper summarized the research of hot forging die both domestic and abroad,mainly introduced the Failure Forms of hot forging die and the impact of the thermal stress on the life-span of hot forging die.Then,introduced the development,theory and processing methods of high frequency calefaction cladding technique.The second part of this paper designed an experiment of plasma cladding.The Substrate material W6Mo5Cr4V2 is one of the chamber near surface layer of hot forging die gradient materials.Cladding in the same parameters of the high-frequency conditions,with different ceramic powder and self-fluxing alloy powder ratio and different powder block thickness,the corresponding sample coatings had been obtained through the high-frequency induction heating.And then carried out on the micro-sample analysis,including microscopic analysis of metallography,X-ray diffraction analysis,microhardness testing,as well as to elect a reasonable proportion of the powder material,as well as pre-cladding thickness of powder block.At the same time,the three thermal properties parameters of the coatings(thermal expansion coefficientα,thermal coefficient k and specific heat capacity c) were measured,and the measured results are analyzed and discussed,selected the most outstanding of the melting parameters coating sample.The third part of the test results into a comprehensive analysis,to draw the relevant conclusions.Cladding layer thickness of powder pre-block,the different cladding powder ratio on the microstructure of the cladding layer,microhardness and thermal parameters have very important implications.Other conditions in certain circumstances,the cladding layer thickness T= 1.5mm,as a result of excessive melting of the matrix material,the cladding layer to increase the surface hardness is very small,will not achieve the effect of surface hardening.Cladding layer thickness T=3mm can be relatively high surface hardness of the cladding layer,can play the role of surface hardening.Alloy cladding powder coating ratio on the microstructure,microhardness and thermal parameters have great impact.Powder block in the preset thickness T= 3mm,powder ratio of 15%/85%,25%/75%and 35%/65%(MoSi₂/Ni60A),the hardness of the coatings increases,and the cladding layers are relatively dense,in which the number of rigid dispersed phase particles is gradually increased,and there is a good metallurgical bonding between the cladding and steel substrate.The powder ratio of 45%/55%(MoSi₂/Ni60A) of the cladding layers are obvious defects,the coating micro-hardness value is not stable,and between the cladding layer and the steel substrate it does not form a good metallurgical bonding layer.Finally,the thermal expansion coefficientα,thermal coefficient k and specific heat capacity c of 25%/75%and 35%/65%(MoSi₂/Ni60A) coating are determined,through analysis and comparison of measured values obtained that the integrated thermal physical properties of the cladding layer in ratio of 35%/65%are superior to the cladding layer's in ratio of 25%/75%.Comprehensive test results showed that when the thickness T=3mm of the cladding layer,and the ratio of the cladding layer of powder to 35%/65% (MoSi₂/Ni60A),the cladding layer has the organization of dense,high hardness,a good metallurgical bonding with steel substrate and superior thermal parameters, which can be proved high frequency induction cladding is an effective way to obtain the ceramic-reinforced metal matrix cladding of chamber surface of hot forging die.