• KSTLE International Journal
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• 제3권1호
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• pp.38-42
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• 2002

Diamond-like Carbon(DLC) films were deposited on Si wafers by an RF-plasma-assisted CVD using CH$_4$gas. Tribological tests were conducted with the use of a rotating type ball on a disk friction tester with dry air. This study made use of four kinds of mating balls that were made with stainless steel but subjected to different annealing conditions in order to achieve different levels of hardness. In all load conditions, testing results demonstrated that the harder the mating materials, the lower the friction coefficient was. The friction coefficients were fecund to be lower with austenite mating balls than with fully annealed martensite balls. Conversely, the high friction coefficient found in soft martensite balls appeared to be caused by the larger contact area between the DLC film and the ball. The wear tracks on DLC films and mating balls could prove that effect. Measuring the wear track of both DLC films and mating balls revealed a similar tendency compared to the results of friction coefficients. The wear rate of austenite balls was also less than that of fully annealed martensite balls. Friction eoefficients decrease when applied leads exceed critical amount. The wear track on mating balls showed that a certain amount of material transfer occurs from the DLC film to the mating ball during a high friction process. Raman Spectra analysis Showed that the transferred materials were a kind of graphite and that the contact surface of the DLC film seemed to undergo a phase transition from carbon to graphite during the high friction process.

• 한국표면공학회지
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• 제36권2호
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• pp.116-121
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• 2003

Ti-Si-N coating layers were deposited onto WC-Co substrates by a hybrid system of arc ion plating (AIP) and sputtering techniques. The tribological behaviors of Ti-Si-N coating layers with various Si contents were investigated by the dry sliding wear experiments, which were conducted at three different sliding speeds, 0.1, 0.3, 0.5 m/s, against the steel and alumina balls. In the case of steel ball, the average friction coefficient slightly decreased with increasing the sliding speed regardless of Si content due to adhesive wear behavior between coating layer and steel ball. At constant sliding speed, the average friction coefficient decreased with increase of Si content. On the contrary, in the case of alumina ball, the average friction coefficient increased with increasing the sliding speed regardless of Si content, indicating that the abrasive wear behavior was more dominant when the coating layers slide against alumina ball. Through these experimental results, it was found that the tribological behaviors of Ti-Si-N coating layers were effected by factors such as Si content, sliding speed, and kinds of counterpart materials rather than the hardness of coating layer.

• 대한기계학회논문집A
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• 제26권2호
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• pp.260-266
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• 2002

DLC films were deposited on Si wafer by RF plasma assisted CVD using CH4 gas. Tribological tests were conducted using rotating type ball on disk friction tester in dry air. Four kinds of mating balls were used. The mating balls were made with stainless steel but apply different annealing conditions to achieve different hardness conditions. Testing results in all load conditions showed that the harder the mating materials, the lower the friction coefficient among the three kind of martensite mating balls. In case of austenite balls, the friction coefficients were lower than fully annealed martensite ball. The high friction coefficient in soft martensite balls seems to be caused by the larger contact area between DLC film and ball. The wear tracks of DLC films and mating balls could have proven that effect. Measuring the wear track of both DLC films and mating balls have similar tendency comparing to the results of friction coefficients. Wear rate of austenite balls were also smaller than that of fully annealed martensite ball. The results of effect of applying load showed, the friction coefficients were become decrease when the applying loads exceed critical load conditions. The wear track of mating balls showed that some material transfer occurs from DLC film to mating ball during the high friction process. Raman spectra analysis showed that transferred material was a kind of graphite and contact surface of DLC film seems to undergo phase transition from carbon to graphite during the high friction process.

• Tribology and Lubricants
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• 제33권4호
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• pp.141-147
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• 2017

The vibration data of bearings are very useful for monitoring and determining the condition of the bearings. The defect frequencies of ball bearings have been used for monitoring there condition. However, it is not easy to verify the defect frequencies as the wear progress. Therefore there is a need for an easy method to monitor the damages of bearings in real-time and to observe the variations in vibration characteristics as the wear progress. In this study, a bearing test equipment is constructed to diagnose the damage of bearings. The friction coefficient and vibration data are measured by using a torque sensor and an acceleration sensor, and the correlation between the measured data is analyzed to diagnose the condition of the bearing. We reached the following conclusions from the results. When the ball surface, inner and outer rings of a ball bearing are damaged, the friction coefficient increases to over 0.02 with an adhesion on the surface. Moreover this damage occurs more quickly with an increase in the number of revolutions. In the vibration characteristics, the amplitude of vibration wave appears high with an increase in the friction coefficient. In the high frequency range between 1000 and 2000 Hz, a wide range of frequency components with high amplitude occurs continuously irrespective of the number of revolutions.

• Tribology and Lubricants
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• 제39권6호
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• pp.228-234
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• 2023

In this study, reciprocating wear tests are performed on AISI 52100 bearing steel to investigate its tribological behavior in a hexagonal boron nitride (h-BN) water solution. The h-BN-based aqueous lubricant is prepared using an atoxic procedure called ultrasonic sonication in pure water. Ball-on-flat reciprocating sliding experiments are conducted, where the ball is slewed on a fixed flat at 50-㎛ displacement. The lubricating behavior of h-BN is compared with that of deionized (DI) water. Results show that the friction coefficient is higher in h-BN testing than that in DI tests, but the results are equalized as the friction coefficient reaches a stable level. Scanning electron microscopic images reveal significant material loss in the center and mild abrasion on the edge of the wear scar in h-BN tests. However, these effects are minor in DI water situations. The results of energy-dispersive X-ray spectroscopy show that considerable oxidation occurs in the central zone of the wear scar in h-BN cases with strong adhesion and material removal. These findings reveal the importance of determining ideal circumstances that can tolerate material friction and wear.

• 대한기계학회논문집A
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• 제27권3호
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• pp.335-342
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• 2003

In this study, the effects of oxide layer formed on the contact parts of TiN coated ball and steel disk in sliding are investigated. Also wear mechanism to from the oxide layer and the characteristics of the oxide layer formation are investigated. AISI 52100 steel ball is used for the substrate of coated ball specimens. Two types of coated ball specimens were prepared by depositing TiN coating with 1 and 4 ${\mu}{\textrm}{m}$ in coating thickness. AISI 1045 steel is used for the disk type counter-body. To investigate the effect of oxide layer on the contact parts of the two materials, the tests were performed both in air for forming oxide layer on the contact parts and in nitrogen environment to avoid oxidation. And to study the effects of surface roughness of counter-body, TiN coating thickness and contact load of sliding test on the characteristics of oxide layer formation on counter-body, various tests were carried out. From the results, the friction characteristics between the two materials was predominated by iron oxide layer that formed on wear track on counter-body and this layer caused the high friction. And the formation rate of the oxide layer on wear track increased as the real contact area between the two materials increased as the contact load increased, the TiN coating thickness decreased and the surface of counter-body smoothened.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제34회 추계학술대회 개최
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• pp.109-116
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• 2001

In this study, the effects of oxide layer formed on the contact parts of TiN coated ball and steel disk in sliding are investigated. Also wear mechanism to form the oxide layer and the characteristics of the oxide layer formation are investigated. AIS152100 steel ball is used for the substrate of coated ball specimens. Two types of coated ball specimens were prepared by depositing TiN coating with 1 and 4um in coating thickness. AISI1045 steel is used for the disk type counter-body. To investigate the effect of oxide layer on the contact parts of the two materials, the tests were performed both in ambient for forming oxide layer on the contact parts and in nitride environment to avoid oxidation. And to study the effects of surface roughness of counter-body, TiN coating thickness and contact load of sliding test on the characteristics of oxide layer formation on counter-body, various tests were carried out. From the results, the friction characteristics between the two materials was predominated by iron oxide layer that formed on wear track on counter-body and this layer caused the high friction. And the formation rate of the oxide layer on wear track increased as the real contact area between the two materials increased as the contact load increased, the TiN coating thickness decreased and the surface of counter-body smoothened.

• Tribology and Lubricants
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• 제38권1호
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• pp.15-21
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• 2022

Diamond reinforced Cr-based coating has been proposed as wear-resistant materials. In this study, the friction and wear characteristics of diamond reinforced Cr-based coating are experimentally assessed. The experiments are performed using a pin-on-reciprocating plate tribo-tester under various normal forces with boundary lubrication. The stainless-steel ball is used as a counter material. Prior to the experiments, mechanical properties such as elastic modulus and hardness are determined using nanoscale instrumented indentation. The hardness of the specimen is further determined using a Vickers hardness tester. The specimens before and after the experiments are carefully observed using a confocal microscope to understand the wear characteristics. In addition, the wear volume and wear rate of the specimens are determined based on the confocal microscope data. The results show that the friction coefficients are 0.096-0.100 under 20-40 N normal forces. Furthermore, the wear rates of the diamond reinforced Cr-based coating and the stainless steel ball under 20-40 N normal forces are found to be 12.8 × 10^-8 mm³/(Nm)-15.5 × 10^-8 mm³/(Nm) and 1.9 × 10^-8 mm³/(Nm)-3.9 × 10^-8 mm³/(Nm), respectively. However, the effect of the normal force on wear rates is not clearly observed, which may be associated with the flattening of the ball. The results of the study may be useful for the tribological applicability of diamond reinforced Cr-based coating as wear-resistant materials.

• 열처리공학회지
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• 제27권2호
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• pp.65-71
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• 2014

SMF9060 material is a Fe-based powder sintered alloy that is used for several automobile components such as Synchronize Hub, oil pump and transmission. These components are required excellent wear resistance and durability. In this study, we have performed a dry wear test at the ambient air and Ar gas conditions in the room temperature, and a lubricant wear test at the room temperature and engine oil temperature of $100^{\circ}C$. The amount of wear volume and coefficient friction are measured by a Profilometer and a Ball on disk type wear tester. The wear volume in Ar gas condition was a little higher than that in the ambient air condition. However the wear volume in the lubricant wear condition was much lower than in the dry wear condition. XRD analysis of the debris in Ar gas condition showed that the oxide film was not formed.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.20-25
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• 1996

The needs to machine hardened steels with high productivity and good surface integrity have been increased in the dies ＆ molds industry. This paper presents some experimental results on the CBN ball endmilling for hardened tool steel. This investigation concerns on the effects of cutting speed and cutting fluids on the cutting performance such as cutting forces, tool wear, and surface finish. The wear of CBN ball endmill for each cutting conditions were also examined through the microscopic observation. It has been found out that the higher cutting speeds with cutting fluids result in better cutting performance.