Effect Of Silicon On Structures And Properties Of High Chromium Cast Iron Welding Layers Prepared By High Frequency Induction Cladding

As a kind of surface strengthening technology for metal material,high frequency induction surfacing has many advantages,such as fast heating?small heat affected zone? simple technology and so on.High chromium cast iron is a kind of commonly used wear resistant material.Ithas the advantages of cost-effective and wide adaptability.In this paper,the effect of silicon content on the microstructure and properties of high chromium cast iron surfacing layer was studied by adding a certain amount of silicon element in high chromium cast iron alloy.In order to optimize welding process parameters,the operating current?heating time ? flux additionwere studied with orthogonal experiment in this paper.The optimized parameters were as follow: operating current: 70A?heating time: 50s?flux addition 14%.The influence of silicon content in the powder on the formability of the surfacing layer was studied by using the above parameters.The results show that when the silicon content is more than 7%,the formability is poor.The high frequency induction surfacing layer of silicon content with 0.6%,1%,2%,3%,4%,5%and 7% was prepared by the optimized process.Using optical microscopy?SEM?EDS?XRD?Rockwell hardness tester?Vickers hardness tester?wear testing machine for testing and analysis the microstructure and properties of surfacing layer were researched.The results are as follows:The microstructure of the surfacing layer is hypereutectic high chromium cast iron with a primary carbide and eutectic structure.Both primary and eutectic carbides are M7C3 type carbides,and the matrix is composed of martensite,austenite and ferrite.When the silicon in the surfacing alloy powder increases from 0.6% to 7%,its content in the surfacing layer changes from 0.286% to 2.083%.With the increase of the amount of silicon in thepowder,the amounts of primary carbides in surfacing layers increase and morphology was refined.The number of eutectic carbides decreases and the interval between the eutectic carbidereduces.The number of silicon atoms dissolved in the matrix increases;the austenite content in matrix decreases,the content of martensiteincreases.Analysis on the macro and micro hardness of surfacing layer were carried out.The high chromium cast iron surfacing layer of Rockwell hardness is between 59.2~63.7HRC.With the increase of the amount of silicon,the hardness of surfacing layer increased but when the silicon content is more than 5%,the hardness of surfacing layer increases gently.High chromium cast iron surfacing layer of primary carbide Vickers hardness value is 1310.6~1383.1HV,not change with the amount of silicon.The Vickers hardness of Eutectic structureincreases from 590.5 to 691.6HV.With the increase of the amount of silicon the Vickers hardness value increased.When the amount of silicon is more than 4%,the increasing trend is flat gradually.The fracture toughness of surfacing layer is analyzed.With the increase of the silicon content in the powder,the fracture toughness of the surfacing layer increases firstly and then decreases.When the amount of silicon is in the 0.6%~5%,with the increase of the amount of silicon,the fracture toughness of surfacing layer also increases.The fracture toughness of surfacing layer reaches the highest value when the silicon content is 5%;when the silicon content was 6%~7%,with the increase of the amount of silicon,the fracture toughness of surfacing layer decreases.The wear resistance of the surfacing layer was analyzed,and the wear resistance of the surfacing layer was characterized by the relative wear resistance.When the load is 10 N,with the increase of the amount of silicon,the relative wear resistance of the surfacing layer increases and the maximum value is 1.14.When the amount of silicon is more than 5%,the relative wear resistance increases slowly.When the load is 40 N,with the increase of the amount of silicon,the wear resistance of the surfacing layer increased firstly and then decreased.When the silicon content is 4% relative wear resistance reached 1.11.According to the above test results,considering the economic performance and wear resistance of the surfacing process,it is confirmed that the appropriate amount of silicon in high chromium cast iron powder is 4%.