Research On The Properties Of Ni Coated TiC Particles Reinforced H13Steel Composite By Powder Metallurgy

ABSTRACT:H13steel, which is one of the most widely used hot-work die steel materials in our country, has good room and high temperature mechanical properties. The property of H13is expected higher with the expanding of industrial application of H13. Thus there is a great application value for the material used in special conditions if particulate reinforced materials based on H13can be prepared by powder metallurgy. In this paper, H13composites reinforced by Ni coated TiC particles were prepared by powder metallurgy technology. The influence of ball milling process and sintering process on the properties of composites were investigated. Microstructure, TiC distribution and the bonding interface of the composites were analyzed. Density, sintering property, mechanical property of the composites were studied by using the devices of X-ray diffraction, scanning electron microscope, thermal gravity analysis, micro hardness tester, mechanical testing machine and the thermal simulation testing machine.And the high temperature deformation behavior of H13composites were researched through hot pressing experiment, The results obtained are as following,(1)Through the study of the process of ball milling. It came to a conclusion that high-energy ball milling process had a great effect on the performance of compound powder. Over the process of ball grinding, the granularity of powder particles refined to about20microns, the morphology changed from spherical into irregular piece of chip shape. The compacting formability became better. Also the sintering process of compound powder became easier, as the powder particle size refined,the specific surface increased, and also produce a lot of defects, strain, which reduced the powder reaction activation energy, promoted the sintering process. At the same time, high-energy ball milling could make the TiC particles dispersed more evenly in the composites.(2)According to the sintering kinetics equation, it was concluded that nickel plating on the surface of TiC particles was advantageous to the sintering process of composites. The best sintering parameters of H13 steel composites was1400℃for2hours. Under the condition of the optimal sintering process, the H13steel substrate, adding nickel plating TiC particles as reinforced, could effectively improve the comprehensive performance of materials; At room temperature, the hardness of material increased from462HV to496HV; The tensile strength increased from1069MPa to1337MPa; Whereas the impact toughness and plasticity declined.(3)During the processes of hot compressed, not only the composites had plastic deformation but also the density of material increased. For the stress strain curve, with the strain rate increasing, the stress of H13composites compressed in high temperature were also increasing. In low strain rate, the flow curves were smooth. However, in high strain rate they were fluctuating. According to the relative material parameters obtained from the compression experiment, the deformation constitutive equation of H13composites describing the relationship of yield stress peak value,strain rate and temperature was given as following:(4)Based on the principle of thermal processing map, high temperature compressed deformation data was used to obtain the processing maps of H13composites under the maximum50%deformation. It showed that the processing temperature of H13composites was1050-1150℃and the strain rate was1-10s-1,and in1050℃/10s-1the composites had highest power dissipation and good thermal formability.