• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.399-400
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• 2006

M390 microclean(R) of $B{\ddot{o}}hler$ Edelstahl is a powder metallurgical plastic mould steel with a high level of corrosion and wear resistance and therefore often used in the plastics processing industry. But as a consequence of rapidly advancing developments in the plastics processing industry the required level of wear resistance of tool steels in this field is constantly rising. For that reason a new PM tool steel with higher hardness values and an increased amount of primary carbides has been developed to improve the resistance against abrasive and adhesive wear. The wear resistance of both steels against adhesive situations for components of the plastification unit of injection moulding machines has been tested with a novel method. In case of processing polyolefins with an injection moulding machine it was found that there is adhesive wear between the check-ring and the flights of the screw tip of the non-return valve under certain circumstances. The temperature in that region was measured with an infrared temperature sensor. The existence of significant peaks of that signal was used as an indicator for an adhesive wear situation.

• Tribology and Lubricants
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• v.35 no.2
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• pp.139-147
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• 2019

This study investigates the effects of corrosion resistance characteristics of opponent materials in relative motion on the sliding wear behavior of mild carbon steel. Pin specimens made of mild carbon steel are tested at several sliding speeds against mating discs made of two types of alloyed steels, such as type D2 tool steel (STD11) and type 420 stainless steel (STS420J2), with different corrosion resistance characteristics in a pin-on-disc type sliding wear test machine. The results clearly show that the sliding wear behavior of mild carbon steel is influenced by the corrosion resistance characteristics of the mating disc materials at low sliding speeds. However, the sliding wear behavior at high sliding speeds is irrelevant to the characteristics because of the rising temperature. During the steady state wear period, the sliding wear rate of mild carbon steel against the type 420 stainless steel at a sliding speed of 0.5 m/s increases considerably unlike against the type D2 tool steel. This may be because the better corrosion resistance characteristics achieve a worse tribochemical reactivity. However, during the running-in wear period at low sliding speeds, the wear behavior of mild carbon steel is influenced by the microstructure after heat treatment of the mating disc materials rather than by their corrosion resistance characteristics.

• 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.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.876-881
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• 2001

DLC(Diamond-like carbon) films possess high hardness, low friction coefficient, and good wear resistance. Due to these properties, DLC films have been used extensively in magnetic hard disk industry. The objective of the present study was to investigate the influence of environmental condition on the tribological behavior of DLC coated hard disk. It is found that the tribological characteristics of DLC films are strongly affected by relative humidity and temperature. Specifically, the friction coefficient increases with increase in temperature at relative humidity of 50%. However, at 20% and 85% RH the effect of temperature was not significant. Also, the degree of wear could be observed using an AFM.

• Tribology and Lubricants
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• v.16 no.3
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• pp.194-200
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• 2000

In order to evaluate the effect of Nb on wear properties of high speed steel(HSS) by powder metallurgy, niobium-alloyed HSS have been prepared by adding 0%, 1%, 3% and 5%Nb to HSS of 6%W-5%Mo-4 %Cr-5%V-5%Co. Sliding wear tests were conducted at various sliding speed conditions under the constant pressure using a pin-on-disc type machine. The results of this study show that the wear resistance of HSS by powder metallurgy was increased by the addition of Nb within the range of sliding speed used in this experimental study. However, the amount of Nb did not improve the wear resistance. It may be due to the thermal stability of carbide and high temperature properties of the matrix containing Nb comparing to that without Nb.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.265-271
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• 1998

High temperature wear behavior of plasma sprayed zirconia based coating sealing with zirconia sol were investigated for high temperature wear resistance application. The zirconia powders containing 2.5, 5.0, 7.5, 10.0 mol% of MoS$_2$, $Fe_2O_3$ for plasma spray were made by spray drying method. As-sprayed coating was sealed by zirconia-sol to fill up the pore and crack in coating. wear test were performed at temperature ranges from room temperature to 600$\circ$C. The microstructural changes of before and after sealing process were examined by SEM, XRD and EPMA. After sealing process, the porosity was decreased and micro-hardness was increased. The wear properties of coating after sealing process were improved by sealing of pores and cracks. The behavior of wear amount and coefficient of friction were same tendency to before sealing process.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.5
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• pp.559-566
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• 2014

Plasma coatings have been conducted to improve the mechanical properties of thermal resistance, wear resistance, corrosion resistance and thermal shock with respect to Great-Bar which is used as a carrier device for ironstone sintering under $700^{\circ}C$. The surface coatings on the upper side of the Great-Bar exposed on extreme environments of high temperature, severe wear, corrosion and thermal shock extended the life time due to the barrier coating layer. $Al_2O_3$, $Cr_2O_3$, WC coatings were applied to Great-Bar and their mechanical and chemical properties are analyzed by several experimental tests such as thermal resistance, wear resistance, corrosion resistance and thermal shock resistance. It shows excellent advantages with respect to wear, thermal shock and corrosion.

• Tribology and Lubricants
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• v.35 no.1
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• pp.24-29
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• 2019

In this work we investigated the friction and wear characteristics of a magnesium alloy, which has been receiving much attention as a light metal in industrial applications such as automobiles and aerospace. Magnesium is one of the lightest structural material that has high specific strength, lightweight, low density and good formability. However, current issue of using magnesium alloy is that magnesium has weakness against temperature. As the temperature increases, magnesium undergoes poor creep resistance and ease of softening, and therefore, its mechanical strength decreases sharply. To solve this issue, a new type of magnesium alloy that retains high strength at high temperature has been proposed. The tribological behavior of this alloy was investigated using a tribotester with reciprocating motion and heating plate. A stainless steel ball was used as a counter surface. Results showed that extrusion process has similar wear behavior to the commonly used casting process but retains good mechanical strength and durability. The presence of an alloying element enhanced the wear properties especially in high temperature. This study is expected to be utilized as fundamental data for the replacement of high density materials currently used in mechanical industries to a much lighter and durable heat-resistant materials.

• Composites Research
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• v.16 no.3
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• pp.75-84
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• 2003

The purpose of this study is to investigate the wear properties of Saffil/Al, Saffil/A12O3/Al and Saffil/SiC/Al hybrid metal matrix composites fabricated by squeeze casting method. Wear tests were done on a pin-on-disk friction and wear tester under both dry and lubricated conditions. The wear properties of the three composites were evaluated in many respects. The effects of Saffil fibers, $\textrm{Al}_2\textrm{O}_3$ particles and SiC particles on the wear behavior of the composites were investigated. Wear mechanisms were analyzed by observing the worn surfaces of the composites. The variation of coefficient of friction(COF) during the wear process was recorded by using a computer. Under dry sliding condition, Saffil/SiC/Al showed the best wear resistance under high temperature and high load, while the wear resistances of Saffil/Al and Saffi1/$\textrm{Al}_2\textrm{O}_3$/Al were very similar. Under dry sliding condition, the dominant wear mechanism was abrasive wear under mild load and room temperature, and the dominant wear mechanism changed to adhesive wear as load or temperature increased. Molten wear occurred at high temperature. Compared with the dry sliding condition, all three composites showed excellent wear resistance when lubricated by liquid paraffin. Under lubricated condition, Saffil/Al showed the best wear resistance among them, and its COF value was the smallest. The dominant wear mechanism of the composites under lubricated condition was microploughing, but microcracking also occurred to them to different extents.

• Journal of the Korean Vacuum Society
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• v.4 no.S2
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• pp.100-105
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• 1995

Nitrogen implantation process has been applied for improvement of wear resistance of Zircaloy-4 fuel cladding materials. Nitrogen was implanted at 120keV to a total dose range of $1\times 10^{17}$ions/$\textrm{cm}^2$ to $1\times 10^{18}$ions/$\textrm{cm}^2$ at various temperatures between $270^{\circ}C$ and $671^{\circ}C$. The microstructure changes by nitrogen implantation were analyzed by XRD and AES and wear behavior was evaluated by performing ball-on-disc type wear testing at various loads and sliding velocities under unlubricated condition. Nitrogen implantation produced ZrNx nitride above $3\times 10^{17}$ions/$\textrm{cm}^2$ as well as heavy dislocations, which resluted in an increase in microhardness of the implanted surface of up to 1400 $H_k$ from 200 $H_k$ of unimplanted substrate. Hardness was also found to be increased with increasing implantation temperature up to 1760 $H_k$ at $620^{\circ}C$. The wear resistance was greatly improved as total ion dose and implantation temperature increased. The effective enhancement of wear resistance at high dose and temperature is believed to be due to the significant hardening associated with high degree of precipitation of Zr nitrides and generation of prismatic dislocation loops.