Steel Matrix Composites Research Articles

Fabrication of steel matrix composites locally reinforced with different ratios of TiC/TiB 2 particulates using SHS reactions of Ni–Ti–B 4C and Ni–Ti–B 4C–C systems during casting

Steel matrix composites locally reinforced with different molar ratios of in situ TiC/TiB 2 particulates (2:1, 1:1 and 1:2, respectively) have been fabricated successfully utilizing the self-propagating high-temperature synthesis (SHS) reactions of Ni–Ti–B 4C and Ni–Ti–B 4C–C systems during casting. Differential thermal analysis (DTA) and X-ray diffraction (XRD) results reveal that the exothermic reactions of the Ni–Ti–B 4C and Ni–Ti–B 4C–C systems proceed in such a way that Ni initially reacts with B 4C and Ti to form Ni 2B and Ti 2Ni compounds, respectively, with heat evolution at 1037 °C; Subsequently, the external heat and the evolved heat from these exothermic reactions promote the reactions forming TiC and TiB 2 at 1133 °C. In the composites reinforced with 1:2 molar ratio of TiC/TiB 2, almost all TiB 2 grains have clubbed structures, while TiC grains exhibit near-spherical morphologies. Furthermore, TiB 2 grain sizes decrease, with the increase of TiC content. In particular, in the composites reinforced with 2:1 molar ratio of TiC/TiB 2, it is difficult to find the clubbed TiB 2 grains. Macro-pores and blowholes are absent in the local reinforcing region of the composites reinforced with 1:1 and 1:2 molar ratios of TiC/TiB 2, while a few macro-pores can be observed in the composite reinforced with 2:1 molar ratio of TiC/TiB 2. Moreover, the densities of the composites reinforced with 1:1 and 1:2 molar ratios of TiC/TiB 2 are higher than that of the composite reinforced with 2:1 molar ratio of TiC/TiB 2. The composite reinforced with 1:2 molar ratio of TiC/TiB 2 has the highest hardness and the best wear resistance.

TiB 2 and TiC stainless steel matrix composites

Stainless steel matrix composites reinforced with TiB 2 or TiC particulates have been in situ produced through the reactive sintering of Ti, C and FeB. X-ray diffraction analysis confirmed the completion of reaction. The TiB 2, TiC and steel were detected by X-ray diffraction analysis. No other reaction product or boride was found, indicating the stability of TiB 2 and TiC in steel matrix. The SEM micrographs revealed the morphology and distribution of in situ synthesized TiB 2 and TiC reinforcements in steel matrix. During sintering the reinforcements TiB 2 and TiC grew in different shapes. TiB 2 grew in hexagonal prismatic and rectangular shape and TiC in spherical shape.

Effect of Fe content in Fe–Ti–B system on fabricating TiB 2 particulate locally reinforced steel matrix composites

In situ TiB 2 particulate locally reinforced steel matrix composites were successfully fabricated by self-propagating high-temperature synthesis (SHS) reactions in a Fe–Ti–B system containing 10, 30, 50 and 70 wt.% Fe, respectively, in the molten high chromium alloy steel during casting. The locally reinforced regions of the Fe–TiB 2 composites with different Fe contents in the Fe–Ti–B system consist of three different regions, i.e. the Fe-rich region, the fine TiB 2 particulate region and the larger TiB 2 particulate region. The portion of the Fe-rich region decreased and the larger TiB 2 particulate region became unclear with the increase in Fe content in the Fe–Ti–B system. In addition, only a small amount of micropores is found in the fine TiB 2 particulate region of the Fe–TiB 2 composite synthesized in a 70Fe–Ti–B system, and the Fe content has obvious effect on the wear resistance of the locally reinforced region of the Fe–TiB 2 composites.

Abrasive wear properties of metal matrix composites produced by hot isostatic pressing

Steel matrix composites are an attractive choice for paper, pulp and mineral crushing industries because of their wear resistant properties. In this paper the abrasive wear properties of the tool steel matrix composites are studied. The rubber wheel abrasion tests were carried out using six different composites. The tool steel Ralloy ® WR6 was used as matrix material in all composites. Typically there is about 20 vol% VC in the matrix before the addition of the particle reinforce- ments. Reinforcements were either cemented carbides (WC-Co), cast tungsten carbides (WC) or niobium carbides (NbC). All the composites were so-called double dispersion composites having two distinctive reinforcement types. Although the wear resistance of the composite materials has been found to increase with reinforcement additions in rock crushing environment with multimode wear conditions, the pure abrasion resistance of the composites, having up to 30% additional reinforcements, was found inferior to the matrix tool steel. Based on the observations it is suggested that in order to improve the abrasive wear resistance of the tool steels by adding hard particles, the matrix-particle interface s hould be strong enough to prevent the detachment of particles and the amount of particles should be high enough to compensate the accelerated wear of the matrix because of hard particle wear debris.

Fabrication of steel matrix composites locally reinforced with in situ TiB2–TiC particulates using self-propagating high-temperature synthesis reaction of Al–Ti–B4C system during casting

Abstract Steel matrix composite locally reinforced with in situ TiB2–TiC particulates was successfully fabricated utilizing the self-propagating high-temperature synthesis (SHS) reaction of Al–Ti–B4C system during casting. Microstructure characterization of the composites reveals that the microstructure is made up of two types of TiB2 and TiC particulates concerning particulate size and distribution and white Fe-rich regions. Moreover, the results show that the hardness and wear resistance of the composites are higher than those of the steel matrix.

In situ synthesis of TiB 2–TiC particulates locally reinforced medium carbon steel–matrix composites via the SHS reaction of Ni–Ti–B 4C system during casting

The fabrication of medium carbon steel–matrix composites locally reinforced with in situ TiB 2–TiC particulates using self-propagating high-temperature synthesis (SHS) reaction of Ni–Ti–B 4C system during casting was investigated. X–ray diffraction (XRD) results reveal that the exotherm of 1042 °C initiated by heat release of the solid state reaction in the differential thermal analysis (DTA) curve is an incomplete reaction in Ni–Ti–B 4C system. As-cast microstructures of the in situ processed composites reveal a relatively uniform distribution of TiB 2–TiC particulates in the locally reinforced regions. Furthermore, the particulate size and micro-porosity in the locally reinforced regions are significantly decreased with the increasing of the Ni content in the preforms. For a Ni content of 30 and 40 wt.%, near fully dense composites locally reinforced with in situ TiB 2 and TiC particulates can be fabricated. Although most of fine TiB 2 and TiC particulates which form by the reaction–precipitation mechanism during SHS reaction are present in the locally reinforced region, some large particulates which form by the nucleation–growth mechanism during solidification are entrapped inside the Fe-rich region located in the reinforcing region or inside the matrix region nearby the interface between matrix and reinforcing region. The hardness of the reinforcing region in the composite is significantly higher than that of the unreinforced medium carbon steel. Furthermore, the hardness values of the composites synthesized from 30 to 40 wt.% Ni–Ti–B 4C systems are higher than those of the composites synthesized from 10 to 20 wt.% Ni–Ti–B 4C systems.

HVOF thermal sprayed coatings on aluminium alloys and aluminium matrix composites

This project is concerned with the investigation of the capability of HVOF thermal spraying to improve the tribological and mechanical properties of aluminium alloys and aluminium matrix composites (AMCs). The present study describes and compares the mechanical and tribological properties of CCr–NiCr and WC–CoCr thermal sprayed HVOF coatings deposited on three different substrates: steel, aluminium alloy and aluminium matrix composite. The coating microstructures were characterised by SEM and optical microscopy. Differences in roughness have been determined by profilometry. The ultra-microindentation technique was applied to measure the hardness and the elasto-plastic properties of the coatings. Experiments using a tribometer (pin on disc configuration) under lubricated and dry conditions have been performed in order to evaluate the friction and wear properties of the different systems. The morphology of the wear tracks after pin on disc tests was characterised using SEM microscopy and profilometry with the aim of studying the wear mechanism.

Fabrication of Steel Matrix Composite Locally Reinforced with in Situ TiB2 Particulate using Self–Propagating High–Temperature Synthesis Reaction of Ni–Ti–B System During Casting

The medium steel matrix composites locally reinforced with in situ TiB2 particulates synthesized by SHS reaction of Ni–Ti–B system during casting are successfully fabricated. Microstructural characterization shows that the size of TiB2 particulate and amount of micro‐porosity in composite are decreased with the increasing of Ni content in Ni–Ti–B system. The wear resistances of composites are higher than those of medium steel and high Cr steel.

Reactive infiltration synthesis of TiB 2–TiC particulates reinforced steel matrix composites

The reactive infiltration synthesis of steel matrix composite reinforced with in situ TiB 2–TiC particulates by the self-propagating high-temperature synthesis (SHS) reaction of the Ni–Ti–B 4C system during casting was investigated. The as-cast microstructures of the in situ processed composites reveal a uniform distribution of TiB 2–TiC particulates with a fine size of ∼5.0 μm. Although, microstructural characterization shows the absence of macro-pores and blowholes, the Ni content in the system has a significant effect on the presence of micro-porosity in the composites. Moreover, the results show that the densities of the composites are lower than those of medium carbon steel and high-speed (HS) steel. Although, the hardness values of the composites are significantly higher than that of medium steel and lower than that of HS steel, the wear resistance values of the composites are higher than those of medium steel and HS steel.

In situ Synthesis of TiB2 Particulate Locally Reinforced Steel Matrix Composite by the Self-propagating High-temperature Synthesis Reaction of Al-Fe-Ti-B System during Casting

In-situ TiB2 particulate locally reinforced steel matrix composites were successfully fabricated by the self-propagating high-temperature synthesis (SHS) reaction of 10Al-20Fe-Ti-B and 40Al-20Fe-Ti-B systems, respectively, in the molten high chromium alloy steel during casting. Microstructure analysis of the composite showed that the interface bonding between the matrix and locally reinforced region is very good and the locally reinforced region consists of three different regions, i.e. the Fe-rich region, the fine dispersion of TiB2 particulates region and the larger TiB2 particulates region. The wear test showed that the wear resistance of the locally reinforced regions of the composites is higher than that of the steel matrix.

Development and characterisation of high-speed steel matrix composites gradient materials

Powder metallurgy (P/M) offers the advantage to obtain a composite material with a high content of reinforcement and, consequently, with a big hardness as well as the possibility of changing the composition as a function of the requirements. The materials developed in this work are constituted by a high-speed steel (HSS) matrix core and composite materials with this matrix and gradient concentration of NbC reinforcement, from the core to the surface, through different steps. Composite powders of different content in NbC were produced through high energy milling in order to obtain the gradient composition. These powders were characterised in their morphology and microhardness. The materials were processed through conventional P/M techniques, pressing and sintering. The behaviour of the final materials was studied by means of the microhardness profile and bending strength, showing a high increment in this one by means of the gradient composition.

Development of particle reinforced steel matrix composites : W.S. Lin, Y.Y. Li. (South China University of Technology, Guangzhou, China.) PM Industry, Vol 11, No 5, 2001, 25–29. In Chinese

The interfacial property between TiB2 particles and the ferrite matrix in a steel matrix composite (SMC) fabricated by eutectic solidification was investigated by nanoindentation. The significant work hardening of TiB2/ferrite interface before interfacial debonding during deformation has been revealed for the first time in this new class of SMC. Such interfacial plasticity, proven by the high dislocation density generated and stored at the TiB2/ferrite interface, is responsible for the excellent ductility of this class of SMC.

Effect of intermetallic particles on wear behaviour of stainless steel matrix composites

Metal matrix composites were manufactured using 316L austenitic stainless steel as matrix and TiAl intermetallic as reinforcement. Three levels of reinforcement were used: 3, 6 and 9 % (vol.). Composites were made by P/M: mixing, uniaxial pressing and sintering. The sintering was carried out in vacuum, at three temperatures (1120, 1200 and 1250 °C). The influence of the addition of the intermetallic on the microstructure of the stainless steel was assessed by a complete metallographic study using optical and scanning electron microscopy, coupled with a semi-quantitative microanalysis. Wear behaviour was evaluated by a ‘pin on disk’ test. Materials were tested against tool steel, and the main test conditions were as follows: 5 N load, <30% moisture, 0.1 m/s speed, and 377 m sliding distance. X-ray diffraction of powder debris was also studied and wear tracks were observed by SEM.

Influence of reinforcement volume fraction on sliding wear behaviour of SHS derived ferrous based metal matrix composite

Steel matrix composites reinforced with (W,Ti)C particles were processed by directaddition of an innovative powder to molten 0.4 wt-%Clow alloy steel.Thispowder was producedusing a self-propagatinghightemperature synthesis(SHS) reaction and consisted of a dispersion of fine (W,Ti)C particles (5-10 μm) in an iron binder. Dry unidirectional sliding wear behaviour ofthe compositematerialanditsunreinforced counterpartwas investigated atroomtemperature against a white cast iron counterface. In situ monitoring of wear and friction, in conjunction with electron microscopy, has been used tointerpretwearscar microstructures observed intermsofwear mechanisms. Wear experimentswere performedat a sliding speed of 1.5 m s-1 at different test loads. It was found that the wear resistance of the composite material was superior to that of their unreinforced counterparts over the entire range of loading employed during this investigation. The unreinforced base alloy exhibited a transition from mild to severe wear at a load of approximately 70 N. No such transition was found to occur for the composite materials. Instead, after a transient period of running in wear, steady state conditions were observed. At the highest level of carbide addition this transient period did not occur and the composite wore in a regime of mild wear over the full spectrum of loading utilised.

Atmosphere Influence on Sintered 316L Austenitic Stainless Steel Matrix Composites Reinforced with Intermetallic and Carbide Particles

Atmosphere Influence on Sintered 316L Austenitic Stainless Steel Matrix Composites Reinforced with Intermetallic and Carbide Particles

Interactions between tungsten carbide (WC) particulates and metal matrix in WC-reinforced composites

A variety of experimental techniques have been used to investigate the interactions between tungsten carbide (WC–Co 88/12) particulates and the matrix in some new wear resistant cobalt-based superalloy and steel matrix composites produced by hot isostatic pressing. The results show that the chemical composition of the matrix has a strong influence on the interface reaction between WC and matrix and the structural stability of the WC particulates in the composite. Some characteristics of the interaction between matrix and reinforcement are explained by the calculation of diffusion kinetics. The three-body abrasion wear resistance of the composites has been examined based on the ASTM G65-91 standard procedure. The wear behavior of the best composites of this study shows great potential for wear protection applications.

Elevated temperature sliding wear behaviour of TiC-reinforced steel matrix composites

TiC-steel matrix particulate composites were processed by direct addition of powder to molten BS970:070M15 steel. This powder was produced using a self-propagating high-temperature synthesis (SHS) reaction and consisted of a dispersion of fine TiC particles (5–10 μm) in an iron binder. Dry reciprocating sliding wear behaviour of the composite material and its unreinforced counterpart was investigated at room temperature, 250 and 500°C against a white cast iron counterface. In situ monitoring of wear, in conjunction with electron microscopy, has been used to interpret wear behaviour in relation to the wear scar microstructures observed. Wear experiments were performed at an average sliding speed of 0.1 m s −1 at different test loads. At room temperature, both materials exhibited a marked increase in wear rate at a particular load, indicative of a transition to a more severe regime of wear. This occurred at a significantly higher load for the TiC-reinforced composite than for the unreinforced steel. Prior to the onset of this transition, the reinforced steel displayed significantly superior wear resistance. Above this transition load, however, the reinforced material exhibited similar wear rates to those of its unreinforced counterpart. At a test temperature of 250°C, the transition to the more severe wear regime was observed to occur at a substantially higher load for the TiC-reinforced steel than for the unreinforced material. At 500°C, wear at the interface is dominated by oxidation and both materials exhibited mild wear (characterised by extremely low wear rates) over the range of loads considered in these experiments.

Synthesis of titanium and tungsten carbides in iron matrices

Carbides, TiC and WC, having high melting points and high hardness, are effective reinforcements in steel and iron. In fact, their steel and iron matrix composites have been commercially applied as wear resistant materials. Usually, these composites are produced by a powder metallurgy route, which is complex and costly [1, 2]. Undoubtedly, cost effective production of these composites will extend their commercial application. Stir casting process is attractive in economy and simplicity, and is widely employed in production of metal matrix composites with low melting points such as aluminum and magnesium etc. [3]. But, it is hardly applied to steel matrix composites because of their high melting points. Recently, in situ production of metal matrix composites has received much interest worldwide. Its eminent advantage is that it eliminates interface incompatibility of matrices with reinforcements by creating more thermodynamically stable reinforcements based on their nucleation and growth from the parent matrix phase. The technique was exploited to synthesize TiC reinforcing steel and iron matrix composites [4, 5]. Particulate TiC was successfully synthesized in liquid iron by addition of ferrotitanium or titanium filing to ironcarbon alloy melts. In situ formed TiC reinforcements are spherulitic and distributed uniformly in the matrices. The result is encouraging. However, it should be noted that there is great difference in density between TiC and iron alloy melt. Relatively light TiC particulates may float up during a large-scale production resulting in their uneven distribution in casting. On the other hand, no work was conducted on in situ synthesis of WC, an important reinforcement, in iron melt. Different from TiC, WC is heavier than iron. Therefore, it may sink down in the melt. But, (TiW)C phase, whose density is between those of TiC and WC, may be more prospective candidate for reinforcements synthesized in situ in steel and iron melts. The present work tried to synthesize in situ TiC, WC and (TiW)C in iron matrices, respectively, and examined their microstructural characteristics. It is expected that the preliminary results can be significant in promoting the development of in situ synthesized steel and iron matrix composites. Commercial powders of titanium, tungsten, graphite and iron were used for the preparation of the batches. The batches, Fe-16wt%Ti-4wt%C, Fe-18.8wt%W1.2wt%C and Fe-8wt%Ti-9.4wt%W-2.6wt%C, respectively, were prepared to obtain 20 wt% TiC-Fe, 20 wt%

Review on TiC reinforced steel composites

Particulate reinforced ferrous-based metal matrix composites exhibit both excellent wear and cutting properties, and can give significant cost reductions over existing materials used in heavy wear applications. This paper reviews the current status of literature on titanium carbide–reinforced steel matrix composites and looks into the different types and methods of reinforcements being used, together with other alternative processing routes. Mechanical properties such as elastic modulus, low and high temperature strengths and wear properties are discussed as a function of the volume fraction of reinforcement. The review concludes by underlining the importance of further research in some critical areas to fully realize the industrial potential of these composites.

Ecotechnology for high-speed tool steels

The ecotechnology for high-speed steels produced during the entire metallurgical process is discussed in this paper. Various eco-technologies, including thin-strip casting and comprehensive utilization for the steels, are developed to meet the needs of different types of high-speed tool steel. The as-cast strips were of 2.5–4.0 mm thickness, reduced by hot rolling to 1.8–2.0 mm thickness. The steel sheets were used to make power hacksaw blades. Cutting tests revealed that the performance of these hacksaw blades was satisfactory, compared with that of hacksaw blades made of conventionally produced steel sheets. The recycled utilization of alloying elements in steel scales, oxides, and grinding wastes was carried out. A systematically comprehensive technology of this steel was studied and developed, in which the steel scales were recycled in a closed-loop, the oxides were utilized by self-propagating high temperature reclamation, and the grinding wastes were prepared in a special de-oxidizer and high-speed tool steel matrix composite. These detailed processes are comprehensively introduced in the paper.