| High chromium cast iron with Cr7C3 as the hard phase has excellent wear resistance,and is widely used as an anti-abrasive wear material in the industrial field.High-chromium cast iron surfacing materials are often used to improve the wear resistance of the workpiece surface.The surfacing metal has high hardness and excellent wear resistance,but it has high brittleness and poor crack resistance.In this paper,two flux-cored welding strips of high-chromium cast iron reinforced with TiC and ternary boride are designed to further improve the wear resistance and crack resistance of the surfacing metal.Using optical microscope(OM),scanning electron microscope(SEM),X-ray diffractometer,micro-hardness and wear test and other methods,the amount of TiFe,Mo,B,rare earth added to flux-cored welding strip TIG arc cladding surfacing metal was studied The influence of microstructure and performance,and the theoretical analysis of the formation mechanism of the composite hardened Cr7C3 hard phase,etc.,provides technical data for the design of composite strengthened high-chromium cast iron surfacing materialsThe main phases of the surfacing metal with TiFe added to the flux-cored ribbon are M7C3,(Cr,Fe)7C3,NiCrFe and TiC.When TiFe is not added,M7C3 in the surfacing metal is coarse,unevenly distributed,and the number is small.After adding TiFe,M7C3 has been refined to different degrees,the size of the hard phase is reduced,the distribution of the hard phase is more uniform,and the number is increased.The statistical calculation results based on Imagepro Plus software show that the volume fraction of the hard phase of the surfacing metal with 3.5%TiFe addition is 67.10%,and the average size of the hard phase of the surfacing metal with 5.2%TiFe addition is 14.02?m.The Fe-Cr-Ti-C alloy phase diagram analysis,mismatch calculation and thermodynamic calculations prove that TiC synthesized in situ in the liquid metal can be used as the heterogeneous nucleation core of Cr7C3,reducing the nucleation resistance of Cr7C3,making Cr7C3 Refine.The TiC particles that are not the nucleation core of the primary carbide may also refine the primary carbide by hindering the free growth of the primary carbide.The average microhardness of the surfacing metal with 5.2%TiFe added is the highest,which is 1078.7HV,which is 560.1%higher than that of the substrate Q235.The weight loss of surfacing metal mills with TiFe addition amount of 0%,1.7%,3.5%and 5.2%were 8.2mg,5.4mg,3.6mg and 2.5mg,respectively.Under the same test conditions,the maximum weight loss of the surfacing metal grinding with 0%TiFe addition is 8.2 mg,and the minimum weight loss of the surfacing metal grinding with 5.2%TiFe addition is 2.5 mgThe test results of adding Mo and B to the high-chromium cast iron flux-cored welding tape show that the Mo2FeB2 ternary boride is formed through the welding metallurgical reaction,and the surfacing metal strengthened by the composite strengthening of Mo2FeB2 and Cr7C3 is obtained.The addition of B4C transition B to the flux-cored welding tape has better strengthening effect on the surfacing metal than the addition of FeB.The addition of Mo and B in the flux-cored welding strip affects the phase composition of the surfacing metal.The main constituent phase of the surfacing metal with 43%Mo is Cr7C3,Mo2FeB2,FeCrNi and MoCrFe;the surfacing metal with 34.4%Mo addition is mainly The constituent phases are Cr7C3,FeCrNi and FeCrMo,and Mo2FeB2 is not formed.Compared with those without Mo and B,the number of hard phases in the surfacing metal added with Mo and B is significantly increased,the size of the hard phase is also significantly reduced,and the distribution is more uniform.When the amount of Mo added is 43%,38.7%,34.4%,30.1%and 0%,the average microhardness of the surfacing metal is 1105.4 HV0.5,1034.4 HV0.5,853.8 HV0.5,807.9HV0.5 and 650.3 HV0.5 respectively The average microhardness of the surfacing metal with HV0.5 and Mo addition of 43%is the highest,which is 7.2 times that of the substrate Q235.The weight loss of surfacing metal mills with the addition of Mo at 0%,43%,38.7%,34.4%and 30.1%were 9.2mg,2.4mg,2.6mg,5.1mg and 5.7mg,respectively.Under the same test conditions,the maximum weight loss of surfacing metal grinding with 0%Mo addition is 9.2 mg,and the minimum weight loss of surfacing metal grinding with 43%Mo addition is 2.4 mg,which is a significant improvement over the substrate Q235.Thermodynamic calculations show that the Fe-Cr-C-Mo-B surfacing metal alloy system is in the temperature range of 200 0C-3000?,and the Gibbs free energy ?G of MoB,CrB2,CrB,Fe2B and other binary borides is less than Zero,can spontaneously nucleate,the stable Mo2FeB2 ternary boride generated from binary boride hinders the growth of Cr7C3 hard phase,and its growth is inhibited;in addition,the remaining surface active element B in the liquid phase will be adsorbed on The grown Cr7C3 hard phase surface forms a thin film,which hinders the supply of atoms needed for its growth.The above two aspects make the Cr7C3 hard phase significantly refined.The addition of 1%-3%rare earth Mg-Si alloy to the Mo2FeB2 and Cr7C3 composite reinforced flux-cored welding tape increases the number of hard phases of the surfacing metal and reduces the size.When the amount of rare earth Mg-Si is 2%,the number of hard phases is the largest,the size is the smallest,and the refinement effect of the hard phase is the most obvious;when the amount of rare earth is 3%,the hard phase becomes coarse and refined The effect is weakened.The average microhardness of the surfacing metal with the addition amount of rare earth Mg-Si of 0%,1%,2%and 3%is 1105.7 HV0.5,1119 HV0.5,1197 HV0.5 and 1136 HV0.5,rare earth Mg-Si average microhardness of the surfacing metal with 2%Si added is the highest,which is 91.3 HV0.5 higher than that without the rare earth Mg-Si... |
PDF Full Text Request