Research On Situ Preparation And Mechanical Properties Of Cast Iron Surface Titanium Carbide Dense Ceramic Layer

In this paper,titanium carbide dense ceramic layer reinforcing gray cast iron matrix surface composites materials were successfully prepared vis the method of in situ reaction.Besides the microstructure,phase constitution and distribution of elements were analyzed by means of SEM,XRD,EDX and other detection techniques.The formation process and mechanism for preparing titanium carbide dense ceramic layer by in situ were discussed.Moreover,The relationship of the dense ceramic layer thickness,the holding time and heat treatment temperature were discussed by thermodynamics,kinetics and diffusion theory;and Hardness and Elastic Modulus of composites were measured by nanoindentation technique,while the elastic-plastic deformation behavior of materials in nanoindentation process was investigated;Combining with microindentation technique and the correlation parameter of residual indentation,the fracture toughness,crack propagation behavior and toughening mechanisms of the dense ceramic layer were analyzed.Research indicates:(1)Titanium plate and gray cast iron as raw materials,at 1200?insulation for20min,then incubated at 1150,1160,1170?for 1,2,3,4,5h to heat treatment reaction,the titanium carbide dense ceramic layer reinforced gray cast iron matrix surface composites can be prepared finally.Dense ceramic layer mainly consist of Ti C,Graphite,Ti,and?-Fe phase.The relationship of dense ceramic layer thickness(d),the holding time(t)and the holding temperature(T)suits the following equation:(?).(2)The microstructure of reaction layer with varied holding time show different characteristics.The reaction layer is composed of massive particles(5-10?m),columnar particles(3-5?m)and spherical particles(1-3?m);clearly boundary can be seen between the particles each other.(3)The advantages of in-situ reaction were displaied in clean and pollution-free binding interface of Ti C reinforced phase and matrix.(4)The results of EDS indicates:the direction of the residual titanium?dense ceramic layer?matrix,Ti element gradient lower.C element gradually increasing in the dense ceramic layer,but decreasing in the matrix region.Fe element shows a gradient reduce trend from the area of matrix to residual titanium.The formation mechanism of dense ceramic layer can be summarized as"diffusion-in situ reaction-diffusion"process.(5)The hardness of titanium carbide dense ceramic layer on the longitudinal section is 28.82GPa,elastic modulus is 640.15GPa.And the hardness of cross-section is20.91GPa,elastic modulus is 471.32GPa.In addtion,the theoretical breaking strength of longitudinal section is 64.02GPa,and cross-sectional theoretical breaking strength is47.13GPa.(6)By the study of micro-indentation,titanium carbide dense ceramic layer longitudinal section micro-hardness is 3027.08 HV_0.1,about 11 times of substrate.Titanium carbide dense ceramic layer longitudinal section have a higher fracture toughness,Kc value is between 18.81?20.87MPa.m^1/2.