• Journal of Korea Foundry Society
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• v.24 no.2
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• pp.108-114
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• 2004

$Al_2O_3$, SiC reinforced Al matrix composites were fabricated by centrifugal spray casting method and their wear resistance characteristics have been studied. Particles are generally uniformly distributed in the microstructure of as-cast specimens. In order to investigate the effect of secondary deformation, hot rolling was performed for each specimen of pure Al matrix composites with a reduction of 10, 20, 30, 40 and 50% at $400{\sim}500^{\circ}C$, respectively. Microstructure of specimen showed that particle distribution density and hardness increased because of increasing of reduction ratio. Wear test with a various sliding velocity of 1.98, 2.38, 2.88 and 3.53m/sec showed that the wear resistance characterization of composite improved remarkably compared to the normal alloy and performs without reinforced particles. Microstructural observation for the worn surface of pure Al specimens without particles showed that a change in wear mechanism seemed to separate layer by surface fatigue. In other case of Al composite reinforced with $Al_2O_3$ and SiC, the grinder type of wear mechanism was shown.

• Journal of Welding and Joining
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• v.19 no.5
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• pp.506-511
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• 2001

Weld overlay has been developed to improve the property of material surface which is used in the severe environment. Weld overlay is the process which uses an arc heat and welds different composition of alloy on the substrate for the improvements of heat resistance and wear resistance. Weld overlay has a lot of advantages which are high hardness, good processing efficiency, easy controlling of layer thickness, good quality and low cost. In this study, weld overlay was performed by MAG welding on the base metal(SS400) with filler metal which contain composite powders(Cr+C+Mn+Mo+NbC) and solid wire(JIS-YGW11). Characterization of hardness and wear resistance were analyzed by EDS, EPMA, XRD and observations of microstructure were performed to investigate characteristics of overlays. The experimental results of overlaid specimens manufactured with Cr+C+Mn+Mo+NbC powders were obtained as fellows. ${\alpha}-phase$, M(Fe, Cr)3C and NbC of overlays were increased with decreasing the wire feed rates and increasing powder feed rates. Also the hardness of overlays were increased and the specific wear were decreased.

• Journal of the Korean institute of surface engineering
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• v.27 no.3
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• pp.134-142
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• 1994

$Al_2O_3$coatings on mild steel substrate by plasma spray process were produced to evaluate microstructural characterization and mechanical properties. As-coated $Al_2O_3$coating samplessd were subjected to two heat treat-ment conditions : ⅰ) annealing under vacuum circumstance, ⅱ) hot press treated condition. The two heat treat-ed coatings were investigated in terms of microhardness, adhesion strength, wear resistance, porosity forma-tion, and microstructures. In the case of the coatings which were subject to preparation step ⅰ, the porosity in the coating was decreased with the increase of temperature ($700^{\circ}C$-$1100^{\circ}C$), and the wear resistance, microhardnesss and adhesion strength were increased with the increase of temperature. On the other hand, in the case of the coatings which were subject to preparation step ⅱ, wear resistance and adhesion strength were improved with the increase of temperature and pressure. Experimental measurements of coatings which were produced by both preparation conditions were enhanced compare to those of as-coated coatings.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.7
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• pp.1619-1629
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• 1995

The Al/Al$_{2}$O$_{3}$ SiC and Al/Al$_{2}$O$_{3}$/C hybrid metal matrix composites (MMCs) were fabricated by squeeze infiltration method. Uniform distribution of reinforcements were found in the microstructure of metal matrix composites. Mechanical tests were carried out under various test conditions to clearly identify mechanical behavior of MMCs, and the wear mechanism of Al/Al$_{2}$O$_{3}$/(SiC or C) hybrid metal matrix composites were investigated. The tensile strength and hardness of hybrid composites was resulted in increasing compared with those of the unreinforced matrix alloy. Wear resistance was strongly dependent upon kinds of fiber, volume fraction and sliding speed. The wear resistance of metal matrix composites was remarkably improved by the addition of reinforcements. Especially, the wear resistance of the hybrid composites of carbon fibers was more effective than in the composites reinforced with alumina and SiC whiskers of reinforcements. This was due to the effect of carbon fiber on the solid lubrication. Wear mechanisms of hybrid composites were suggested from wear surface analyses. The major wear mechanism of hybrid composites was the abrasive wear at low to intermediate sliding speed, and the melting wear at intermediate to high sliding speed.

• Journal of Korea Foundry Society
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• v.20 no.6
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• pp.377-385
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• 2000

Al matrix composites as the most promising MMCs can be expected to be excellent engineering materials in the nearest future. So as to improve material properties of composite, many manufacturing processes have been developed. Among them, squeeze casting process which offers fine microstructure and near-net-shape is one of the most successful MMCs manufacturing processes. But, in case of with subsieve size particles (under 44 ${\mu}m$), it is very difficult to homogeneously distribute particles in matrix of Al matrix composite by various casting processes, including squeeze casting used so far. Duplex process which was developed in previous study was used to distribute the particle of subsieve size more homogeneously in matrix of Al matrix composite. Microstructures, wear and heat resistance characterization of Al-Si-Cu-Mg-(Ni)/SiCp manufactured by duplex process were examined to clarify the effect of manufacturing conditions, particle size of reinforcement and alloying elements. Al matrix composites reinforced with SiCp(10 ${\mu}m$) have the lowest wear amount among composites reinforced with 3 ${\mu}m$, 5 ${\mu}m$ and 10 ${\mu}m$ SiCp. The wear amount of Al matrix composites with 10 wt.% SiCp(3, 5, 10 ${\mu}m$) was decreased according to the increase of the sliding speed because abrasive wear takes place at high sliding speed of 4m/s and worn debris with block type occurs at low sliding speed of 1m/s. As for heat resistance, it is made clear that remarkable heat resistance property can be obtained by addition of Ni element in Al matrix composites.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.25-29
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• 1998

Sliding wear test and surface characterization techniques such as micro-Raman spectroscopy were employed to determine the effect of whisker content and orientation on the friction and wear behavior of SiC whisker reinforced alumina. Composites containing unidirectionally oriented whiskers were fabricated by novel technique Addition of SiC whiskers up to 20 vol.% lowered the friction and improved wear resistance. The results of this study indicated that highly disordered graphite and size of the layer behind the whiskers were responsible for variation of wear rate and friction coefficient.

• 연구논문집
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• s.33
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• pp.175-182
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• 2003

In this study, the wear resistance of the complex powder diffusion treated KS STD 61 has been investigatived. KS STD 61 tool steel was pretreated in quenching and tempering processes to obtain the tempered martensitic microstructure. The samples were packed with complex powder in steel pot($\Phi$90x60mm) and heated in a box furnace. the complex powder diffusion treatment are carried out at $540^{\circ}C$, $520^{\circ}C$, $500^{\circ}C$ for 40min, 1.5hr and 2.5hr. The microstructure, microhardness, wear resistance, and coating layer thickness of the complex powder diffusion treated samples were investigation. The weight loss of as heat treated sample was 0.4mg and that of the complex powder treated at $540^{\circ}C$ for 2.5hr was 0.17mg. These result means that the wear resistance of tool steels can be easily improved by the powder diffusion process at conventional tempering treatment temperature.

• Nuclear Engineering and Technology
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• v.55 no.4
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• pp.1468-1475
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• 2023

Enhancement of wear resistance of components used in fast reactors is necessary for long service life of the components. Plasma nitriding is a promising surface modification technology to impart high hardness and improved wear resistance of various steel components. This study discusses the characterization of chrome nitrided SS316L casing ring used in secondary sodium pump of fast breeder reactor and its stability under long term sodium exposure. Microstructural and hardness analysis showed that stress relieved component could be chrome nitrided successfully to a thickness of about 100 ㎛. Assessment of in-sodium performance of the chrome nitrided casing ring subjected to long term exposure up to 5000h at 550℃, showed retention of chrome nitrided layer with a case depth almost similar to that before sodium exposure. A slight decrease in the hardness was observed due to prolonged high temperature sodium exposure. Tribological studies indicate very low coefficient of friction indicating the retention of good wear resistance of the coating even after long term sodium exposure.

• Korean Journal of Materials Research
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• v.8 no.12
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• pp.1138-1145
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• 1998

The sliding wear behavior of Ni-base hardfacing alloy, Deloro 50, was investigated at the contact stresses of 15ksi and 30ksi under the various wear environments. In air at room temperature, Deloro 50 showed lower wear resistance than Stellite 6 even at 15ksi due to the occurrence of severe adhesive wear. This seems to be caused by the lower hardness and work- hardening rate of Deloro 50 than those of Stellite 6. In water at room temperature, Deloro 50 showed as good wear resistance as Stellite 6 at 15ksi. It was considered to be due to that water could effectively prevent metal to metal contact through contacting asperities. However, Deloro 50 showed severe adhesive wear at 30ksi in water at room temperature. It seems to be that the water could not suppress adhesion wear at 30ksi. At $300^{\circ}C$ in air, Deloro 50 exhibited higher wear resistance than Stellite 6 even at 30ksi. It was considered that the oxide glaze layers formed on wear surface during sliding, effectively prevented direct metal-to-metal contacts.

• Journal of Powder Materials
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• v.26 no.3
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• pp.214-219
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• 2019

In this study, the microstructure and characterization of an overlay welding layer using Fe-based composite powders are reported. The effects of the number of passes and composition of powders on the microstructure and mechanical properties are investigated in detail. The welding wire and powders are deposited twice on a stainless-steel rod using a laser overlay welding process. The microstructure and structural characterization are performed by scanning electron microscopy and X-ray diffraction. The mechanical properties of the first and second overlay layers are analyzed through the micro-Vickers-hardness tester and abrasion wear tester. In the second overlay layer, the hardness and specific wear are approximately 840 Hv and $2.0{\times}10^{-5}mm^3/Nm$, respectively. It is suggested that the increase of the volume fractions of $(Cr,Fe)_7C_3$ and NbC phases in the second welding layer enhances the hardness and wear resistance.