Preparation And Performance Research Of Bimetal Composite Wear-resistant Plate

The common wear-resistant metal material,high chromium cast iron and wearresistant steel,has been used widely because of its excellent properties of the wear resistance and the hardness.This kind of material is supposed to perform excellent properties in terms of the wear-resistance,the hardness and the impact toughness when it is subjected to repeated impact under certain conditions.However,the common wearresistant metal material is not able to meet these requirements.In this work,a bimetal composite wear-resistant plate with high impact toughness and good wear-resistance was fabricated by utilizing surface liquid sintering method.The microstructure and properties of sintering state of the bimetal composite wear-resistant plate before and after heat treatment have been systematically studied,respectively.The main conclusions are as follows:The bimetal composite wear-resistant plate samples were prepared at 1250℃ by using the surface liquid sintering method in argon atmosphere.P arameter of the holding time has effect on the macrostructure of the samples.The macrostructure analysis demonstrated that the more compact structure of the sample with no macroscopic defects was obtained under optimum sintering condition based on holding time for more than 20 min at 1250℃.The microstructure was analyzed by metallographic microscope.The result indicated that good metallurgical bonding can be obtained between the composite wear-resistant layer and the low carbon layer.There were no cracks,voids and inclusions at the interface.Specifically,the composite wear-resistant layer mainly consisted of carbides(M7C3,M6C),austenitic and pearlite;the size of grain in the low carbon layer significantly grew to 90 μm.A 50 μm thick ferrite diffusion zone appeared in the low carbon layer near the interface,nevertheless a 30μm thick pearlite zone appeared in the composite wear-resistant layer.The SEM showed that carbon atoms diffused from the low carbon steel to the composite wearresistant layer,which was upslope diffusion phenomenon.Moreover,the bimetal composite wear-resistant plate exhibited higher impact toughness(17.5 J/cm2)in comparison of other single high chromium cast iron with wear-resistant property.The maximum interface shear strength reached 632 MPa at the interface.The microhardness distribution of the sample showed an uptrend from the low-carbon steel layer to the composite wear-resistant layer.Besides,the macrohardness distribution in the composite wear-resistant layer was even.It was found to be about 45.3 HRC.After quenching,the martensite transformation occurred in the composite wearresistant layer,which consisted of carbides(M7C3,M6C),martensite,retained austenite and the secondary carbide precipitated from the matrix.When the quenching temperature was increasing,the amount of M7C3 carbide and martensite was increased while the retained austenite was decreased.It was a remarkable increase in the hardness of the composite wear-resistant layer with the quenching temperature increasing.The maximum value of hardness reached 65 HRC at 1040℃.The sample obtained under optimum condition,followed by tempering treatment,demonstrated that the decomposition of martensite in the composite wear-resistant layer consisted of the M7C3,M6C,tempered sorbate.The amount of the secondary carbide rose as the tempering temperature increasing.When the tempering temperature was above 550℃,the aggregation and growth of the M23C6 was observed.The hardness of the composite wear-resistant layer reached the maximum value(57 HRC)at the tempering temperature of 500℃.Further increasing the tempering temperature,the hardness reduced.By comparison,the impact toughness of the tempered samples at different temperature was superior to that of the only quenched sample at 1040℃(prior to tempering treatment).The impact toughness increased first and then decreased with the tempering temperature increasing.The optimum impact toughness was 36 J/cm2 at the tempering temperature of 550℃.In the abrasive wear test,compared with the wearresistant material-Crl6,the wear resistance of the bimetal composite wear-resistant plate samples after heat treatment was much higher.In conclusion,the optimum heat treatment process of the bimetal composite wear-resisitant plant,as noted by the hardness,the impact toughness and the wear-resistance,was found to be 1040℃ for quenching as well as 550℃ for tempering.