Fabrication Of TiC_p Locally Reinforced Austenitic Manganese Steel Matrix Composite By SHS-Casting Route

With the rapid development of modern industry, wear resistant materials need represent good wearability not only on the condition of strong impact, it is also necessary, under the conditions of medium or low stress. The ordinary wear resistant materials have been unable to adapt to rigorous working conditions, therefore, the exploitation of new wear resistant materials has become an important issue to be resolved in the process of industrial production.For a long time, high manganese steel because of high stress, a good strong impact and the wear resistance of metals are widely used in the area of metal wear-resistant materials. However, in the low-stress service environment, high manganese steel with the effect of work hardening inadequately lead to the poor wear resistance appeared. To improve the wear resistance of manganese steel, in particular the wear resistance under the conditions of lack the Surface impact hardening, there was a substantial amount of research work, such as the addition of different alloying elements to improve the original hardness of the high manganese steel and adjust the steel alloy component of high manganese. These modification methods generally tend to undermine the high manganese steel toughness. And austenite manganese steel under the low stress abrasion conditions, using the strong strain hardening ability of the manganese steel metastable austenite not only has better wear resistance, and has good strength and toughness, has a good prospect as a new type of wear resistant material. The hard TiCp is deposited on the surface of austenite manganese steel, not only can increase the wear evidently, but also to ensure strength and toughness and keep the components operating safely and reliably. Even if the surface layer is worn, the matrix still has a high wearability, the wear resistance will continue to play a important role. Therefore, in this paper, the austenite manganese steel has been chosen as the matrix materials.The new in-situ TiCp local reinforced austenite manganese steel matrix composite materials is based on metastable austenite manganese steel, because of the instability of austenite, the martensitic transformation occurred under the conditions of impact or deep-cryogenic treatment. And then the reinforced strengthen of the matrix composites provide a more solid support to the matrix. The TiCp with high hardness and elasticity act as the reinforced body of composite materials, thus achieving the dual strengthen of the matrix and reinforced body. The features of the organization and structure of composite material is that the hard phase (TiC) and the toughness of (Metastable austenitic) combined. One side is the high strength and hardness and wear resistance, the other side is high plastic and toughness and high impact resistant. The contradictions between the hardness and toughness of wear resistant material have a good solution. So the preliminary results have achieved in this thesis:(1) The Thermodynamic analysis of (Ti, Fe) -C system provides a theoretical basis to study the TiCp response by this system. The results show that the thermodynamic stability of TiC is much larger than such as Fe₂Ti, Fe₃C.(2) Use (Ti, Fe)-C system to prefabricate the precast blocks, put into the mold after the pretreatment and use the high-temperature of the molten steel caused SHS reaction, in situ TiCp within the liquid steel molding completed at the same time, effectively avoided the disadvantage of poor wetting plus the particles and the pollution of particle-surface, the poor flow of melt metal and filling difficulties. The volume fraction of the local TiCp reinforced manganese steel matrix composites is successfully fabricated. The TiCp reinforced areas and matrix bonded well, between them there is a transition zone, is useful to improve the bond Strength of "interface". The particles reinforced area is mainly consist of TiCp and matrix steel. The size of TiCp changes between 1μm and 5μm. The majority of the TiCp is nearly spherical shape and the small minority is polygonal or block.(3) Short-term local cryogenic treated on the preparation of the composite samples, make a part of metastable austenite transform to the martensitic, which can be achieved an ideal organization in the austenite+TiCp+martensite layer, hard phase and softening phase combined in the structure. One side is the high strength and hardness and wear resistance, the other side is high plastic and toughness and high impact resistant. In the macroscopic area the internal alloy composition and organizational performance change in a row. Thus it not only can save the reinforced body and resources of precious alloys, and also can solve the contradictions between the toughness and the hardness of abrasion-resistant material.(4) The test on the hardness and wear-resistant of the fabricated composite material:â‘ . Rockwell hardness: The TiCp reinforced and the matrix areas of composite materials without cryogenic treatment exists a larger hardness gap, thereby the boundary bonding become weaker. metastable austenite composite with cryogenic treatment has strengthened the martensitic by transforming to matrix, and slows down the hardness gap of the TiCp reinforced area and the matrix gap, thereby enhancing the bonding strength between the matrix area and TiCp reinforced area.(2). The abrasive wear of disomic static load: Under the different wear conditions study the abrasive wear of composite materials, confirm the failure mechanism of composite materials is microstructure cutting and fatigue spalling, and the microstructure cutting by the abrasive particles happened on the surface of the composite material is chief, then the crack initiation of the plough deformation zone and fatigue spalling leaded by the expansion is supplement.This paper caused SHS reaction of reacting preform used the high-temperature casting of molten steel by combining SHS technology and the traditional casting technology and fabricate the new Local TiCp reinforced manganese steel matrix composites. The iron in (Ti, Fe)-C system and the liquid pressure of the steel dilution is better to solute the causes like the air hole and the densification for the SHS reaction. It expands a new path for the applications field of SHS technology at the point of fabricating the local reiforced particle casting manganese steel composite materials.