Shi Zhong Wei

Preparation Technology of the Low Carbon High Boron Fe-C-B Wear Resistance Steel

The solidified microstructure and the modified treatment have been systematic studied for the low carbon high boron Fe-C-B steel. The cast solidified microstructures of the low carbon high boron steel are consisted of the matrix and the boride phases. The matrix phase is consisted of the ferrite, pearlite and a few martensite phases. The boride phases of the hypoeutectic steel are based mainly on the Fe2B phase. With the increasing of the boron content, the Fe2B phase is decreased. When the boron content is excess 2.6wt.%, the boride phases are changed from the single Fe2B phase to the compound structures. Meanwell, the morphologies of the boride phases are transformed from the long strip-shaped and the fish-bone reticular structure to the rosette type. The boride phases of the eutectic steel are mainly the M2B phase. However, for the hypereutectic steel, it are composed of the M23(C, B)6 and B0.7Fe3C0.3 phases. The suitable modifier for the hypoeutectic low carbon high boron steel is the compound modifier 0.2%RE+0.2%Ti. After modified, the reticular boride phases are disconnected. Moreover, there existed some of isolated massive borides. The appropriate modifier for the hypereutectic steel is the compound modifier 0.9%Nb+0.4%RE. After modified, the primary borides are fine refined and tend to round.

Microstructure and Properties of Mo-Based Composites Reinforced by Al2O3

Mo-based composites with Al2O3 particles were developed in order to enhance the wear resistance of molybdenum alloys. Using Al2O3 power and pure Mo power as raw materials, the Molybdenum powders mixed with Al2O3 particles were prepared using planetary ball mill. And then the Mo-based composites with 3-10vol.% Alumina were prepared by compaction and sintering at 1840°C. The morphology of the Molybdenum powder and microstructure of the composites were analyzed by SEM and XRD. The micro-hardness, density and wear property of composites were researched. The results show that the microstructure of composites is composed of α-Al2O3 particles and Molybdenum matrix. With the increase of Alumina content, the microhardness of Molybdenum matrix increases, and the density first increases and then decreases. The friction coefficient of composite is scarcely affected by the alumina content. While the wear resistance of the composites rises with the increase of Alumina content. The wear failure is caused by abrasive wear characterized by obvious plow furrow and abrasive dust on the worn surface.

Research on Microstructure and Mechanical Properties of High Boron Cast Steel

In recent years, high chromium cast irons have been widely applied in many fields because they have high hardness and abrasion resistance. However, high chromium cast irons are also expensive because much alloying elements, such as chromium, molybdenum and nickel, are added into them. In order to resolve above question, a new abrasion-resistant steel with high boron content was developed in this paper. The new high boron steel, with 0.6%~0.8%B and 0.65% C, was prepared using sand casting method. The microstructure and mechanical properties were researched. The results show that the solidification microstructure of as-cast high boron steel consists of boride (FeB) and matrix composed of pearlite, ferrite, and bainite. And the borides distributes along grain boundary in the form of network. After quenching at 980°C and tempering at 250°C, the FeB transforms to Fe2B, and the matrix transforms lath martensite. The hardness of as-cast high boron steel is 43HRC, and its impact toughness is 5J/cm2. After heat treatment, they increase to 56 HRC and 7J/cm2, respectively, approximating that of high chromium cast irons. The new high boron cast steel have a potential in stead of high chromium cast irons

Effect of Carbon on Frictional Wear Behaviours of High Vanadium High Speed Steel under Dry Sliding Condition

The high vanadium high-speed steel (HVHSS) with about 9wt% vanadium and different carbon contents were prepared using casting process. The effects of carbon on wear properties of HVHSS were studied using pin-on-ring tester, and the failure behaviors were investigated via SEM. Results show the optimal wear resistance is obtained when HVHSS possesses moderate carbon content (2.58wt.%). The cause is that the matrix microstructure of moderate carbon HVHSS is mainly low-carbon lath martensite with good toughness and high hardness, and it can effectively resist micro-cutting and figure wear at the same time, so the role of high-hardness vanadium carbides (VC) can be played enough because of the strong support of matrix. If carbon content is too low, the wear failure of HVHSS is mainly caused by severe micro-cutting and adhesive wear on contact surface because the matrix microstructure of high speed steel is ferrite with very low hardness, which leads to poor wear resistance. While, the matrix microstructure is mainly composed of high carbon martensite with poor toughness when carbon content is too high, therefore, it possesses very poor resistance to cycle fatigue and thermal fatigue, resulting in decrease of wear resistance.

Preparation of Al2O3 Nano-Particles Reinforced Fe-Based Composite Materials via In Situ Synthesis

Al2O3 reinforced iron based composite were prepared via in-situ synthesis with aluminum nitrate, citric acid and iron powder as raw materials, a little C and Mo as additive. The influences of the contents of Al2O3, C and Mo on the microstructure and micro-hardness of the Fe based composites were characterized by XRD, SEM, TEM and micro-hardness tester. The results showed that the Fe-based composite materials with high bonding strength between matrix and Al2O3 can be prepared by in situ synthesis method. The best ratio of the nine Al2O3 particles reinforced Fe-based composite materials in three groups is 3vol. % C, 5vol. % or 7vol. % Al2O3, sintering temperature is 1300°C and quenching temperature is 900°C. The microstructure of the matrix without C addition is ferrite before and after quenching; the microstructure of the matrix with C addition is pearlite before quenching, and the microstructure become to martensite after quenching, the α-Al2O3 and FeC3 are reinforced phases. The microstructure of the matrix with Mo addition is ferrite and FeAl2O4 before and after quenching.

Interface Structure and Properties of Explosive Welded Beryllium Bronze/Steel Composite Plates

In this study, beryllium bronze/steel composite plates were fabricated through explosive welding process using different ratios of explosive. Microstructures of the joint were examined, and then shearing strength, peeling strength, Bending tests and hardness measurements were carried out on the bonded specimens. Experimental studies show that, beryllium bronze and steel could be bonded with a good quality. The interface is wavy texture changing in turns from flat - wavelet - large wave - stable large wave beginning with initiation point. Grains near the interface are elongated parallel to the explosion direction. As the ratio of explosive increase, the amplitude and wavelength of wave are increased, which leads to the increasing of shearing strength and bonging strength. No shearing in the interface is seen from the tensile-shear tests and fracture take place in the low strength material. The bended specimens show that defects such as separation and tearing were not observed. Hardness is increased with increasing explosive ratio and the highest hardness values are obtained near the bonding interface.

Fabrication of Fe-Based Al2O3-TiC Ceramic /Steel Composite by Self-Propagation High-Temperature Synthesis

The Fe-Based Al2O3-TiC Ceramic Composite was fabricated by combining the methods of Self-propagating High-temperature Synthesis with casting. The microstructures of ceramic layer and interface were characterized via SEM, EDS and X-ray diffraction. The Results show that the microstructure of ceramic layer is dense, and the in-situ Al2O3 and TiC particles with size of 1-2 μm are distributed on the ferrite matrix. The hardness of compact ceramic layer reaches 48HRC, and it has graded distribution from ceramic layer to the ferrite matrix. The composite interface between ceramic and matrix is compact, and takes on flexuous. The composite material bonds in a metallographic manner, with high bonding strength.

Influence of Thermite Reaction on the Microstructures and Properties of Cast-Infiltration Composite Layer

Using the steel containing 0.45 percent of carbon as matrix, high carbon ferrochrome as cast-penetrated agent, the steel-based surface composites were fabricated by conventional cast-penetrating process combined with the thermite reaction. The influence of thermite reaction on the microstructures and properties of cast-infiltration layer was researched. The results show that the interfacial bonding is metallurgical fusion between cast-infiltration layer and the matrix under the suitable technological parameters, the thermite reaction during the process of cast-penetrated realizes thermal compensation for liquid metal and improves the mobility of liquid steel by reducing oxidation film of liquid steel surface, consequently increase the thickness of cast-infiltration layer; The ceramic phase of Al2O3 which is generated during the thermite process improves the microhardness of cast-infiltration in a certain extent.

Preparation of Zirconia Nanoparticles in Ionic Liquid –Water and Characterization

Zirconia nanoparticles were prepared in ionic liquid BMIMBF4-water using zirconium salt (ZrOCl2•8H2O), urea as raw material by hydrothermal synthesis method. The structure and morphology of zirconia were characterized by XRD and TEM. The experimental results showed zirconia nanoparticles could be prepared at 170°C for 24 hours in a hydrothermal kettle. Its size was about 10-30nm and the particles dispersed uniformly, and had no agglomeration phenomenon.

Effects of Aging Treatment on Performance of Explosive Welded Beryllium-Bronze/Carbon-Steel Composite Plate

This paper dealt with how the aging time and temperature affected the hardness of beryllium bronze layer in the explosive welded beryllium-bronze/carbon-steel composite plate. The properties of shearing, bonding, cold bending and microhardness were studied in term of the composite plate, including the aging and nonaging. The optimum aging treatment process of the composite plate is aging temperature at 320°C for 3 hours. And the results show that: aging treatment has no obvious effects on the shear strength but sharply decreases bond strength of the composite plate. And aging treatment to a certain extent reduce the cold bending prroperty. After aging treatment, the microhardness value and distribution of carbon steel was no obvious change, and the microhardness of beryllium bronze sharply raised and smoothly distributed.