Study On Mechanical Properties And Wear Resistance Of Al₂O₃p/Steel Hierarchical Composites

Ceramic particle reinforced steel matrix composite is an important development direction of high performance wear-resistant materials.However,there are still many problems in the preparation and application of ceramic particle reinforced steel matrix composites.In terms of preparation,it is difficult to infiltrate ceramic preforms,especially gravity casting.In application,there are some problems such as poor toughness of conventional ceramic particle uniform distribution reinforced composite material（uniform composite material）,easy to occur overall spalling,low wear resistance,poor adaptability to working conditions and so on.Architectureization is a new development direction of high performance composites.Among them,the hierarchical architecture is a composite architecture in which ceramic particles and matrix first form coarser composite particles,and then form the next level of composite materials with matrix,and so on.In this paper,the introduction of hierarchical configuration into wear-resistant steel matrix composites is studied to improve the composite’s comprehensive strength and toughness and wear resistance under impact conditions,which has important theoretical research and application value.The main research contents and conclusions of this paper are as follows:（1）Firstly,Al₂O₃p reinforced high manganese steel and Cr12Mo V tool steel base uniform composites were successfully prepared by micro-powder activated gravity casting infiltration technique.（2）The microstructure,compressive strength plasticity and impact work abrasive wear properties of Al₂O₃p/Mn13 and Al₂O₃p/Cr12Mo V uniform composites were prepared and compared,and the optimized composite matrix was determined.In the homogeneous Al₂O₃p/Mn13 composite,the distribution of Al₂O₃p is more uniform,and the volume fraction is 54.8vol.%.However,there are a large number of reactive interfacial layers（RIL）between Al₂O₃p,the thickest of which is 55.3μm.The hardness of the composite is 55.0HRC and the compressive strength is 278.3MPa.Strain at 3.4%.Fracture analysis revealed that RIL had become crushed during compression.The average wear rate of the composite is 1.38×10^-4cm³/min at the low impact energy of1.5J,and 6.03×10^-4cm³/min at the high impact energy of 3.5J.In Al₂O₃p/Cr12Mo V uniform composite,the RIL of Al₂O₃p cell is significantly reduced,and the maximum thickness is 6.8μm.The hardness of the composite is 62.6HRC,the compressive strength is 1847.9MPa,and the strain is 7.2%.The wear rate at low impact energy is0.68×10^-4cm³/min,and the average wear rate at high impact energy is3.84×10^-4cm³/min.The above studies show that the strength,toughness and wear resistance of Al₂O₃p/Cr12Mo V composites are much better than those of Al₂O₃p/Mn13composites.Therefore,this paper selects Cr12Mo V tool steel as the matrix for further study of composite materials.（3）The adhesion work and tensile tests of Fe-amorphous Na₂Si O₃-Al₂O₃ interface and Fe-Al₂O₃ interface were explored by first principles calculation.The interlaminar adhesion of Fe-amorphous Na₂Si O₃ interface between the 8th and 12th positions is about 434.89J/m²,which is nearly 40 times that of Fe-Al₂O₃ interface.When the strain is 20%,the stress value of Fe-amorphous Na₂Si O₃-Al₂O₃ interface is as high as46.58Gpa,which is 1.5 times that of Fe-Al₂O₃.These results show that the presence of amorphous Na₂Si O₃ significantly improves the bonding performance of Fe-Al₂O₃interface.The interfacial transmission electron microscopy（TEM）study of Al₂O₃p/Cr12Mo V showed that the reactive interfacial layer was amorphous Na₂Si O₃.At the interface without macroscopic reactants,there are amorphous Na₂Si O₃ and Na Al Si₃O₈ at 9.4nm.（4）Secondly,the graded Al₂O₃p/Cr12Mo V steel composite was successfully prepared by gravity casting infiltration technique,in which the II reinforced spheres（composite spheres）were uniformly and discreetly distributed in the matrix.The effects of different II reinforcement sizes（Φ3,Φ5 andΦ7）on the microstructure and mechanical properties of configuration composites were investigated.As the diameter of the composite ball increases,the reactivity interfacial layer between Al₂O₃p decreases,and the hardness of the composite ball increases gradually from 59.0HRC to 66.2HRC.The compressive strength of the composite increases gradually from 1131.8MPa to 2166.8MPa.The compressive strain also increased from 5.8%to 8.5%.Therefore,the graded configuration composite withΦ7composite ball has the best strength and toughness,and its compressive strength and strain are increased by 17.3%and 18.1%compared with uniform composite.The cracks in the hierarchical configuration composites are mainly generated in the matrix,and the composite ball can prevent the crack propagation in the matrix,which leads to the good toughening effect of the hierarchical configuration.The interface of the stageⅡreinforcement makes the dislocation plug to improve the strength.The strengthening mechanism is mainly dislocation shear strengthening mechanism.（5）To further study the different class II reinforced body ball size（Φ3、Φ5 andΦ7）on the architecture of impact abrasive wear resistance of composite materials.Under the abrasive wear condition of 1.0J low impact power,the wear rate of configuration composites decreases from 1.66×10^-4 cm³/min to 1.42×10^-4 cm³/min with the increase of composite ball diameter.The graded configuration composite withΦ7 composite ball has the best wear resistance,because the product of the reactivity interface is the least and the wear resistance is reduced little,but its wear is 108.8%higher than that of the uniform composite.The main wear mechanism of composites is abrasive chiselling,and Al₂O₃p can resist wear.Under the abrasive wear condition of 3.5J high impact power,the wear rate of configuration composite decreases from 6.89×10^-4 cm³/min to 2.58×10^-4 cm³/min with the increase of the diameter of composite ball.The wear resistance of the graded configuration composite withΦ7 composite ball is still the best.Moreover,its wear is32.8%lower than that of uniform composite.The main wear failure mode of composites is Al₂O₃p detachment.