• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 1996년도 제24회 춘계학술대회
• /
• pp.45-54
• /
• 1996

The effect of graphite on the frictional characteristics of Cu-based sintered friction materials was studied by pin-on-disk type wear test. A study has been carried out concerning the optimum concentration of graphite in sintered friction material to obtain the minimum wear rate and low friction coefficient . Friction coefficient and wear rate were increased as increasing the content of graphite in the matrix. In the study the optimum concentration of graphite was 19vol % to get the minimum wear rate and optimal frick'ion coefficient.

• 한국해양공학회지
• /
• 제10권1호
• /
• pp.36-46
• /
• 1996

This paper deals with determinig the proper friction welding condition and analyzing various mechanical properties of friction welded joints of sintered carbide tool materials(K20, P25, and SKDX5 for the blade part of drill or press punch) to alloy steel (SKH4, SCM440 for the shank part of drill or press punch), the alloy steel to aluminum(A6061 for the interlayer material between the blade part and the shank) and sintered carbide tool materials to alumminum. And also acoustic emission test will be carried out during fiction welding to evaluate the weld quality.

• Tribology and Lubricants
• /
• 제23권2호
• /
• pp.66-72
• /
• 2007

[ $MoS_2$ ], is a well-known metal sulfide applied as solid lubricants and an additive to prolong the life of sintered bearings under severe conditions. However, the high price of $MoS_2$ limited its wide application. This study is aimed to investigate the possibility far application to solid lubricants for $Cu_2S$ as a substitute of $MoS_2$. Bronzes added $Cu_2S$ and $MoS_2$, are produced by powder metallurgy in this study, and then evaluated their friction and wear properties., as well as sintered bronze. The sliding wear test using pin-on-disc type machine, was conducted at several sliding speeds for three type test pieces sintered bronzes added $Cu_2S$ and $MoS_2$, and sintered bronze without lubricants. Addition of $Cu_2S$ to bronze leads to relatively good friction properties, although it is not so good as addition of $MoS_2$. However, the wear properies of sintered bronze added $Cu_2S$ are better than that of sintered bronze added $MoS_2$.

• Journal of Welding and Joining
• /
• 제15권2호
• /
• pp.43-53
• /
• 1997

The complete joining method for dissimilar press punch materials and its real-time evaluation method is not available at present. Brazing method has been used for joining them, but it is known that the welded joint by the brazing has the lower bonding efficiency and reliability than the diffusion welding. The friction welding with a diffusion mechanism in bonding was applied in this study. This work was carried out to determine the proper friction welding conditions and to analyze mechanical properties of friction welded joints of sintered carbide tool materials (SKNM50 for the blade part of press punch) to alloy steel (SCM440 for the shank part of press punch) using aluminum (A6061 for the interlayer material) as an insert material between the sintered carbide tool materials and the alloy steel. In addition, acoustic emission test was carried out during friction welding to evaluate the weld quality.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
• /
• pp.975-985
• /
• 2011

Cu-Matrix sintered brake pads and low alloyed heat resistance steel are most applied to basic brake system for high energy moving machine. In this research, we analyzed tribological characteristics for influence of air velocity between disk and pad. At low brake pressure with air flow, friction stability was decreased due to no formation of tribofilm at disk surface. But there are no significant change of friction coefficient at all test conditions. Wear rate of friction materials were decreased with increasing of air flow velocity. In result, air flow velocity influenced friction stability, wear rate of friction materials and disk but not friction coefficient.

• 한국윤활학회:학술대회논문집
• /
• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
• /
• pp.211-212
• /
• 2002

Friction and wear of pressureless sintered Ti(C,N)-WC ceramics were studied using a ball-on-reciprocating flat apparatus in open air. The silicon nitride ball and the cemented carbide (WC-Co) ball were used against the Ti(C,N)-WC plate samples. The friction coefficients of the Ti(C,N)-WC samples against the silicon nitride ball and the cemented carbide ball were about 0.57 and 0.3, respectively. The wear coefficient of the sample without WC addition was 5 times as large as that of the sample with 10 mole % WC addition when tested against the silicon nitride ball under 98 N. The higher wear coefficient of Ti(C,N)-0WC was explained in part by larger grain size. Wear occurred mainly by grain dislodgment after intergranular cracking mainly caused by the accumulated stress within the grains.

• Tribology and Lubricants
• /
• 제12권3호
• /
• pp.48-54
• /
• 1996

Examined in this paper, is the effect of B$_{4}$C addition on the frictional characteristics of Cu-Sn based sintered friction materials. For the specimens 1wt%, 2wt% and 4wt% of B$_{4}$C were added into the reference material. A pin-on-disk type friction tester was used to,measure the friction torque with respect to the surface temperature and sliding distance. Wear mechanism of each specimen is analyzed in the view point of the oxide film formation. The specimen containing 4wt% of B$_{4}$C showed stable friction and low wear since the oxide film was sustained up to higher surface temperature ranges.

• Tribology and Lubricants
• /
• 제31권2호
• /
• pp.42-49
• /
• 2015

Because of the growing need for high-speed transport options such as trains and aircraft, there is increasing demand for technology related to high-speed trains. Among them, braking systems are important in high-speed trains in terms of reliability. Especially, the disk brake system, in use in most high-speed trains, transforms kinetic energy into thermal energy and noise. Therefore, the material properties of both the friction materials and disks are expected to influence the tribological characteristics. In this paper, the tribological characteristics depend on the hardness of the brake disks between the Cu-based sintered metallic friction material and the heat-treated heat-resisting steel disks. A lab-scale dynamometer used to perform braking tests at a variety of braking speeds using dry conditions. The test results revealed that the hardness of the disks affects the friction coefficients, friction stabilities, and wear rates. Thus, the brake system using the heat-resisting steel disk requires proper heat-treatment. These differences are considered to be caused by the change in tribological mechanisms and the generation of an oxide layer on the friction surfaces. The oxide layers on the friction surfaces are confirmed to Fe₂O₃ by x-ray diffraction (XRD) and scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) analysis.

• 대한금속재료학회지
• /
• 제50권11호
• /
• pp.809-815
• /
• 2012

Recently, as the interest in improving energy efficiency has grown, the demand for vehicle and machine parts that are resistant in high temperature corrosive conditions and abrasive environments has increased. Pack chromizing treatment of sintered steels is a profitable method that satisfies both corrosion resistance and low friction properties. Since austenitic stainless steels have good corrosion resistance but low mechanical hardness, if they are replaced by sintered steel parts with pack chromizing treatment, all the desirable properties such as low price, easy molding, high hardness, low frictional coefficient, and high corrosion resistance, can be obtained. The higher corrosion resistance of the chromized parts over that of the austenitic stainless steels was acquired by coating chromium carbides and a thin chromium oxides layer on the surface. Moreover, the surface morphology of chromized parts, which were composed of chromium rich phases and hardened chromium carbides by diffusing and alloying, had a peak-and-valley shape so that the dimple effect by the wrinkled morphology and high hardness induced a low friction coefficient.

• 한국철도학회논문집
• /
• 제12권1호
• /
• pp.72-80
• /
• 2009

소형 다이나모 시험기를 이용하여 4종류의 금속계 소결마찰재와 내열합금 디스크간의 마찰특성을 평가하였다. 고속철도용 소결마찰재는 항공기용 소결마찰재 보다 높은 마찰계수와 마찰계수 안정성을 나타내며, 마모량도 적었다. 또한, 동합금 기지 마찰재는 철계 기지 마찰재보다 마찰면의 온도가 급격히 상승하면 냉각도 빨리 이루어졌다. 시험 후 모든 마찰면에서 Fe 기지의 산화피막이 형성되었고, 산회피막에 따라 마찰특성이 달라졌으며, 마찰면에서는 정상마 모분이 일부가 마찰면 단차부에서 트랩되는 것을 확인하였다.