Wear Properties Of The In-situ TiC,TiC-TiB₂ Particulate Locally Reinforced Manganese Steel Composite

Iron and steel have been widely applied to modern industries as structure materials. Withthe development of science and technology, the conventional materials like iron and steel cannot meet the increasing demands for superior mechanical properties. To solve the problem,scientists intensively studied the steel matrix composites with ceramic reinforcements toachieve a good combination of high strength, toughness and wear resistance. The metalmatrix composites(MMCs) are composite materials with metals and alloys as matrices, theypossess excellence properties such as high specific strength, high specific modulus, excellentwear resistance, high-temperature resistance and are widely used especially under roughconditions. Among all the MMCs, the particulate reinforced MMCs become one of the mostattractive materials in automotive, mining, metallurgy and coal industry.So far, most of the practical MMCs have been reinforced monolithically. However,under many practical working conditions, the part may need optimal combination of manyproperties, i.e. the place where endures the high abrasion, high-temperature and tends tofatigue failure should be distributed by a high volume fraction of ceramic particulates, whilethe place where hardly loads strong action should be the metal matrix with a high toughness.The particulate locally reinforced steel matrix composites using the combustion synthesisduring the casting process in the present study, it has the following advantages: first, itoptimizes the mechanical properties of the composites; second, high volume fraction ofreinforcements can be distributed in the locally reinforced region; third, it saves the valuablereinforcement particulates and reduces the cost.The in situ formed reinforcing particulate is finer in size and their distribution in thematrix is more uniform, yielding better mechanical properties and at the same time thereinforcement-matrix interface is clean, resulting in a strong interfacial bonding. So the in situmethod of fabricating particulate reinforced metal matrix composites have been studied by researchers, aluminium matrix, titanium matrix and magnesium matrix were successfullyfabricated. Moreover, due to the high hardness and thermal stability, good wetting ability andchemical stability with the matrix, TiC and TiB₂ become the most suitable ceramicreinforcement for the metal matrix composites.According to the statement above, in our present study, the high volume fraction of TiCor TiC-TiB₂ particulates locally reinforced manganese steel matrix composites weresuccessfully fabricated using the combustion synthesis during the casting process themicrostructure and wear resistance of the composites are studied.The main research results of the present study are as follows:(1)Using the CS reaction during casting, the TiC or TiC-TiB₂ particulates(the TiC or TiCTiB₂particulates was introduced by Ni-Ti-C/B₄C combustion system) locallyreinforced manganese steel matrix composites were successfully fabricatedï¼›(2)The TiC or TiC-TiB₂ particulates locally reinforced steel matrix composites mainlyconsist of two distinct regions: (I) a TiC or TiC-TiB₂ particulate-reinforced region; (II)a steel matrix region. The interface between the reinforcement and matrix is good andclean; the size of TiC or TiC-TiB₂ particulates in the reinforce region increases withthe increasing of the particulates volume fraction;(3)The hardness value of the in situ TiC or TiC-TiB₂ particulate reinforced region weresignificantly higher than those of manganese steel matrix, and it was increased withthe increasing of the volume fraction of the particulates;(4)The addition of TiC or TiC-TiB₂ reinforce particulates significantly improved thewear resistance of the manganese steel matrix. The reinforced regions with 60vol.%particulate reinforcement presented best wear resistance, compared with the steelmatrix, wear resistance of TiC and TiC-TiB₂ particulates reinforced region increasedby 2.0⁵.1 and 2.2⁶.4 times, respectively;(5)The wear resistance of the TiC-TiB₂ particulates reinforced region was superior to theTiC particulates reinforced region under same condition;(6)As for the manganese steel matrix, there were long, deep and wide grooves on itsworn surface, the deformation of its debris were severe. This indicated mircrocutting was the main wear mechanism for the manganese steel matrix. As for the TiC or TiCTiB₂reinforced regions, the grooves were shallow and narrow on the worn surface,and the amount of grooves was substantially less. Mircrocutting and ploughing wasthe main wear mechanism for the TiC or TiC-TiB₂ reinforced regions.