• Journal of Power System Engineering
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• v.20 no.5
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• pp.5-13
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• 2016

This study is on wear damage of the material for a molding machine that be used at finally cutting of metal beam made in roll forming process of vehicle bump beam process line. SKD11 steel was used with the material for cutting mold jig. In the cutting mold jig, Ti diffusion heat treatment after vacuum heat treatment was carried out for upgrade of surface hardness and anti-wear. Also, the heat treatments by various methods were performed to compare the wear damage degree against above the existing heat treatment. Wear loss and friction coefficient were obtained from wear test. And, micro Vickers hardness values were compared with damaged parts or not of cutting mold jig. Micro Vickers hardness value appeared higher at the undamaged part by Ti diffusion heat treatment. The micro Vickers hardness well followed a two-parameter Weibull probability distribution.

• Journal of Aerospace System Engineering
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• v.11 no.2
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• pp.16-22
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• 2017

This paper investigates fretting wear damage in aerospace, biomedical, and nuclear components. Experimental parameters are identified that affect fretting wear damage. The parameters observed in industries are directly compared. The magnitudes of frequency, relative displacement, and normal force are found to differ depending on the contacting components where fretting wear occurs. In addition, recent solutions to minimize fretting wear damage are reviewed. The solutions include depositing of a low-friction coating, surface treatment, selection of substrate material, and optimal design of contact geometries. This comparative study suggests useful methods and solutions for analyzing fretting wear damage and for designing tribo-components.

• The Korean Journal of Ceramics
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• v.5 no.2
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• pp.155-161
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• 1999

The tribological behaviour of monolithic SiC as well as SiC-TiC and SiC-TiC-$TiB_2$ particulate composite materials has been investigated in unlubricated oscillating sliding tests against $Al_2O_3$ at temperature in the range from room temperature up to $600^{\circ}C$. At temperatures below $600^{\circ}C$ the wear rate of the systems with the composite materials was up to 20 times lower than the wear of the $Al_2O_3$/SiC system and was dominated by the oxidation of the titanium phases. At $600^{\circ}C$ the oxidation rate of the TiC and -TEX>$TiB_2$ grains becomes predominant resulting in an enhanced wear rate of the composite rate of the TiC and TiB2 grains becomes predominant resulting in an enhanced wear rate of the composite materials. The coefficient of friction shows similar values for all materials of investigation, increasing from 0.25…0.3 at room temperature to 0.7…0.8 $600^{\circ}C$. The wear of the $Al_2O_3$/SiC system is mainly abrasive at temperatures above room temperature and is characterised by an enhanced wear of the alumina ball at $600^{\circ}C$.

• Journal of the Korean Society of Industry Convergence
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• v.19 no.4
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• pp.185-192
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• 2016

Low operational cost and high efficiency is absolute requirements in the mass production of the ship engine. Increasing the performance of the fuel injection system in the diesel engine is one kind of solution to improve the efficiency. Modern diesel engines are using electronic control module as the main controller in the fuel injection control system, however the mechanical system still involved in the modern control system. In modern ship engine, a control valve was used in injection fuel to regulate the flow of the fuel. High pressure and friction are intensively occur within this part, therefore high wear resist and low friction coefficient material including fine lubricating are needed. This study is to figure out the wear resist material and proper lubricant in the control valve fuel injection. The experiment has been tested using pin on disk in several treatments those are used various lubricants and non-lubricant condition. Two kinds of lubricant were used in this experiment such as INDERIN AW-32 and paraffin oil. INDERIN AW-32 has a better result compared to non-lubricant condition, which are 20% performance increases than non-lubricant condition. SCM 440 was providing small friction coefficient in the lower velocity. The friction coefficient was constantly maintains at 0.1 m/s of velocity or above respectively with the increment of the loads. Using INDERIN AW-32 and paraffin oil the lowest friction coefficient occurred at the lower load, and increases side by side with the increment of loads.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.362-365
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• 2005

Currently Chemical Mechanical Planarization (CMP) has become an essential step in the overall semiconductor wafer fabrication technology. Especially the CMP pad conditioner, one of the diamond tools, is required to have strong diamond retention. Strong cohesion between diamond grits and metal matrix prevents macro scratch on the wafer. If diamond retention is weak, the diamond will be pulled out of metal matrix. The pulled diamond grits are causative of macro scratch on wafer during CMP process. Firstly, some results will be reported of cohesion between diamond grits and metal matrix on the diamond tools prepared by three different manufacturing methods. A measuring instrument with sharp cemented carbide connected with a push-pull gauge was manufactured to measure the cohesion between diamond grits and metal matrix. The retention force of brazed diamond tool was stronger than the others. The retention force was also increased in proportion to the contact area of diamond grits and metal matrix. The brazed diamond tool has a strong chemical combination of the interlayer composed of chrome in metal matrix and carbon which enhance the interfacial cohesion strength between diamond grits and metal matrix. Secondly, we measured real-time data of the coefficient of friction and the pad wear rate by using CMP tester (CETR, CP-4). CMP pad conditioner samples were manufactured by brazed, electro-plated and sintered methods. The coefficient of friction and the pad wear rate were shown differently according to the arranged diamond patterns. Consequently, the coefficient of friction is increased according as the space between diamonds is increased or the concentration of diamonds is decreased. The pad wear rate is increased according as the degree of diamond protrusion is increased.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.7
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• pp.26-35
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• 2003

This study explains the effects of lubricant and surface treatment on hot forging die life. The mechanical and thermal load, and thermal softening which is happened by the high temperature of die, in hot and warm forging, cause die wear, heat checking and plastic deformation, etc. This study is fur the effects of solid lubricants and surface treatment condition for hot forging die. Because cooling effect and low friction are essential to the long life of dies, optimal surface treatment and lubricant are very important to improve die life for hot forging process. The main factors, which affect die hardness and heat transfer, are surface treatments and lubricants, which are related to thermal diffusion coefficient and heat transfer coefficient, etc. For verifying these effects, experiments are performed for hot ring compression test and heat transfer coefficient in various conditions as like different initial billet temperatures and different loads. The effects of lubricant and surface treatment for hot forging die life are explained by their thermal characteristics. The new developed technique in this study for predicting tool life can give more feasible means to improve the tool life in hot forging process.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.2308-2313
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• 2015

In order to produce an optimal performance solid lubricant used in the refractory slates, various compositions of starch, graphite and water were evaluated by testing their viscosity, coefficient of friction and wear performance. At 15% starch content, the degree of viscosity increment rose in proportional to graphite content and the lowest coefficient of friction was observed when the graphite content was at 30 wt%. Our results demonstrate that, as the water content decrease, the ratio of solid content increases, which compromises the surface coating resulting in increase of coefficient of friction. The best wear test result was obtained when the starch content was at 15 wt% with graphite content at either 25 wt% or 30 wt%.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.5
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• pp.8-15
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• 2018

Films with special properties (e.g., water-repellent films, optical films, anti-reflection films, and flexible films) are referred to as functional films. Recently, there has been interest in fine patterning methods for film fabrication. In particular there have been many studies that use a UV nanoimprint process involving a UV curing method. In this paper, a polymer film was fabricated by the UV nanoimprint process with a micro-pattern, and its durability was evaluated by a wear test and a nano-indentation test. The film mechanical properties (such as coefficient of friction, hardness, and modulus of elasticity) were measured. Moreover, the choice of PUA type resin used in the UV nanoimprint process was confirmed to impact the durability of the thin film. Despite making the polymer film samples using the same method and PUA type resin, different coefficient of friction, hardness, and modulus of elasticity values were obtained. PUA 4 resin had the most favorable coefficient of friction, hardness, and modulus of elasticity. This material is predicted to produce a high durability functional film.

• Tribology and Lubricants
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• v.35 no.6
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• pp.389-395
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• 2019

In various industries, thin film coatings are used to improve friction and wear characteristics. Various types of tribotesters are used to evaluate the friction and wear characteristics of such thin film coatings. In this study, we fabricated a micro-tribotester and Tribo-scanning electron microscopy (SEM) to compare the friction and wear characteristics of copper (Cu) coatings under an atmospheric pressure and a vacuum condition, respectively. The reliability of the different types of tribotesters was evaluated by performing calibrations for the sensor to measure the friction forces and normal loads. Using the two different types of devices, the friction and wear tests are conducted at the same experimental conditions excluding environment conditions such as the atmospheric pressure and vacuum condition. The friction coefficient at the vacuum condition is lower than at the atmospheric pressure. This difference in friction characteristics is due to the fact that wear phenomena occur differently according to the atmospheric pressure and vacuum condition. At the atmospheric pressure, the abrasive wear is the main wear mechanism. At the vacuum condition, the adhesive wear is the main wear mechanism. The reason for the difference in the wear mechanism of the Cu coating at the atmospheric pressure and the vacuum condition is that the oxidation phenomenon, which does not appear at the vacuum condition, occurs at the atmospheric pressure; therefore, the characteristics of the Cu coating change accordingly.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.2
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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.