Fine Particle Bombardment Research Articles

S0301-5-4 FPB前処理を施したDLC被覆部材の摩擦摩耗および疲労特性(軽合金と表面改質処理(2))

In order to clarify the effect of substrate surface on fatigue and tribological properties of steel which were modified diamond-like carbon (DLC) coating which are well known for their excellent tribological properties, fine particle bombardment (FPB) process was performed for pre-treatment before DLC coating process. Wear tests and fatigue tests were carried out. The friction coefficient of the DLC series with FPB process stabilized at low value of about 0.4 though the friction coefficient of Virgin series was higher and fluctuated widely. Furthermore, it is observed that the fatigue strength was increased by DLC coating with FPB process. From the fracture surface observations, it was clear that the fracture origin of the DLC series with FPB process was microbreaks in the coating which were occurred perpendicular to the loading axis and these microbreaks were occurred at early stage because DLC, which has high hardness, cannot deform in unison with the substrate, which has low hardness under cyclic loading.

S0301-5-3 SUP10ばね鋼の疲労強度に及ぼすFPB処理による表面改質効果(軽合金と表面改質処理(2))

The FPB (Fine Particle Bombarding) process attracts attention as a new surface-preparation technique. The effect which the surface modification effect by this FPB process has on the fatigue strength of spring steel was investigated. It proved that surface roughness decreases and the hardness near surface rises rather than a shot peening process as compared with a shot peening process. As a result of comparing the shot time of a FPB process, hardness also increased as the shot time became long. The FPB process showed the value higher than a shot peening process by lowering of surface roughness, and the rise of hardness as a result of the fatigue test. These results showed that the FPB process was effective in the betterment in the fatigue strength of spring steel.

従来のショットピーニングと微粒子ピーニングを組合せた二段ピーニングで付与される残留応力の分布形態とそれが浸炭焼入れ歯車の折損強度に及ぼす影響

従来のショットピーニングと微粒子ピーニングを組合せた二段ピーニングで付与される残留応力の分布形態とそれが浸炭焼入れ歯車の折損強度に及ぼす影響

Removal of NO<I><SUB>x</SUB></I> Using the Reductive Properties of TiO<I><SUB>x</SUB></I> (0<<I>x</I><2)

Removal of NOx is one of the most urgent environmental issues. NO decomposition has been carried out utilizing the reductive properties of TiOx (0<x<2) (i.e., low valence materials of titanium oxides), as represented by Ti-coated Al2O3 balls prepared by fine particle bombardment, or TiOx powders (for example, so-to-speak Ti-black powders used for liquid crystal displays as the black matrix). In the absence of oxygen, NO is found to mostly decompose into NH3 by means of Ti-coated Al2O3 balls or TiOx powders at approximately 150°C, accompanied by traces of N2O. A similar result is also obtained even in the presence of about 20% oxygen. The formation of NH3 is further effective in reducing NO to give water and N2 as shown by the urea-SCR (selective catalytic reduction) system used currently in practice in diesel engines.

OS0711 微粒子衝突処理を施した純チタンの表面組織および疲労特性(構造用材料の疲労挙動と寿命評価,オーガナイズドセッション)

This study was conducted to investigate influence of Fine-Particle Bombarding (FPB) on the microstructure near the surface and fatigue properties of pure titanium. For comparison, a shot-peened material was used. The results showed that surface hardness and compressive residual stress of the FPBed material were higher than those of the shot-peened material. Furthermore, its microstructure near the surface was greatly fined through dynamic recrystallization and nano-crystallized. As a result, the fatigue strength of the FPBed material was improved more than that of the shot-peened material because propagation of intemal cracks to the surface was effectively suppressed by the formed layer.

108 ばね鋼SUP10の疲労強度に及ぼすFPB処理の影響(OS1-2疲労における計測・解析・評価2)

108 ばね鋼SUP10の疲労強度に及ぼすFPB処理の影響(OS1-2疲労における計測・解析・評価2)

Effect of Fine Particle Bombarding on Rolling Fatigue Strength of Carburized Steel

This study is to pilot the future possibilities of the use of the fine particle bombarding (FPB) as the final finishing of the carburized sliding-rolling contact machine elements. In order to evaluate the influence of FPB process on the surface strength of the carburized steel, four kinds of test specimens, which are as-carburized, ground and FPBed ones, were fatigue tested using a thrust rolling bearing type testing machine under a constant loading. The results of the fatigue tests were discussed using the statistic analysis and the observations on the surface properties after the fatigue tests. From the results of both the Weibull plot and the nonparametric test, there was a good possibility that the FPB process after carburizing will be available for the purpose to increase the fatigue life by the improvement of the abnormal layer. The formation of the wear trace of the FPBed disk during fatigue process was different from that of the as-carburized and ground disks, and the FPB process might control the propagation of the fatigue crack due to flaking.

Improvement of Fatigue Strength of Ti-6Al-4V Alloy by Plasma Carburizing and FPB Treatment

This study was conducted to improve fatigue strength of Ti-6Al-4V alloy by hybrid surface modification which was composed of plasma carburizing and fine-particle bombarding (FPB) treatment. Plasma carburizing at the first stage was conducted for 14.4ks at 1023K to form a hardened layer with no remarkable growth of microstructure in the substrate. Subsequent FPB treatment was carried out to eliminate the brittle compound layer (TiC) formed on the outermost surface by plasma carburizing and to introduce compressive residual stress. The result showed that the plasma carburizing slightly increased the fatigue strength of the titanium alloy. However, this treatment greatly reduced fatigue life because fatigue cracks rapidly propagated along the compound layer. When FPB treatment was further performed for the plasma-carburized material, the compound layer was perfectly eliminated and a relatively high compressive residual stress was introduced. As a result, initiation of fatigue cracks from the surface was strongly suppressed so that the crack initiation site existed under the hardened layer. At the same time, the fatigue life and the fatigue strength were greatly improved and the maximum percentage of the improvement in the fatigue strength reached to 30%.

基板表面へのマイクロディンプル形成によるＤＬＣ膜被覆材料の摩擦係数制御

DLC (Diamond Like Carbon) coatings possess many attractive properties, including high hardness, a low friction coefficient, and extreme wear resistance. Due to these properties, DLC coatings have elicited considerable interest within high technological industries, such as those for magnetic hard disks, ball and rolling bearings, high-precision gears, cutting tools, etc.But in some cases, sliding components including car clutches, and laptop hinges require frictional controlled DLC surfaces. They are expected to have appropriate torque, and superior fatigue and wear resistance, but lower friction coefficients are less important.In this study, experiments were conducted on the controlling of frictional forces by topographically structuring contact surfaces. Fine Particle Bombardment (FPB) has been employed to create micro-dimples that act to control surface roughness. The friction coefficient at the DLC surface changes according to the surface roughness.Therefore, the method presented in this study provides a simple and effective way of controlling the friction between DLC coated surfaces in contact.

Improved Adhesion Properties of DLC Film Using Silicon-Carbide Fine Particle Bombardment

The effect of silicon-carbide fine particle bombardment (FPB) was examined as an easy way to improve the adhesion of diamond-like carbon (DLC) films to a substrate. DLC films were deposited on FPB-treated substrates by plasma-based ion implantation and deposition (PBIID) using CH4 and C2H2 as reactant gases. The adhesion force between the film and substrate was evaluated using the critical load as determined by scratch testing. The FPB treatment improved the adhesion about five times and clearly reduced the wear area of the films. Investigation of the reasons for its effectiveness showed that increased surface roughness accounted for about 67% of the improvement, that increased residual stress of the substrate accounted for about 23%, and that an increased ratio of embedded silicon accounted for about 10%.

908 微粒子ピーニング加工が潤滑状態に及ぼす影響の数値解析的検討(機素潤滑設計II)

908 微粒子ピーニング加工が潤滑状態に及ぼす影響の数値解析的検討(機素潤滑設計II)

445 微粒子衝突処理によるナノスケールの結晶を有する層状加工組織の均一形成(T08-2 金属ナノ材料の創製と展開(2) 金属ナノ材料の評価と応用,大会テーマセッション,21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

In this study, the effects of the fine particle bombarding treatment: FPB on crystal structure in the material, were studied. After the FPB treatment, a lamellar work-hardening domain (a lamellar structure) was observed on the specimen surface with the scanning electron microscope: SEM. The crystal orientations in the domain of the lamellar structures were analyzed by the electron backscattered diffraction method: EBSD method with SEM. From the results of Image quality map: IQ map and inverse pole figure map: IPF map obtained by the EBSD method, the several refined crystal grains of sub-micro meter or less in diameter were observed in the lamellar structure. However, the conventional FPB processing locally forms the lamellar structures. In this study, the specimens were moved at the constant speed during the FPB processing and we succeeded in the formation of continuous lamellar structure on specimen surfaces. The observations and hardness test of the microstructure was conducted. The crystal grains in a lamellar structure were nanocrystallized and the hardness in the lamellar structure raised more than 5 times prior to FPB treatment.

Development of Diamond-Like Carbon (DLC) Coating Compatible Surface by Fine Particle Bombardment (FPB)

To improve adhesion of DLC coatings, Fine Particle Bombardment (FPB) treatment using Cr based shot particles was performed. After the FPB treatment, DLC coating process was generated on the Chromium-molybdenum steel. The FPB treatment distributes diffused Cr elements onto the treated surface, creating a Cr-rich layer. The FPB treatment increases the surface hardness and roughness which also affect the adhesion of DLC coatings. Wear test was conducted to compare the tribological properties of the DLC coated FPB treated steels and that of the DLC coated non FPB treated ones. The DLC coated surface, after FPB treatment, kept low friction coefficient, while the DLC coated non FPB treated ones showed a sudden increase due to the delamination of DLC layer. These results imply that delamination of the DLC coating was suppressed by the Cr-rich surface layer created by the previous FPB treatment. Consequently, the applied method was effective to improve the adhesion of DLC coatings.

The Effect of Hybrid Surface Modification; Combination of Fine Particle Bombardment Treatment and Nitriding, on Fatigue Properties of Steel

In order to clarify the effects of the hybrid surface modification process; a combination of Fine Particle Bombardment (FPB) treatment and nitriding, on the fatigue properties of AISI 4135 steel (stress concentration factor: α=2.36), high cycle fatigue tests were carried out with a rotational bending machine at room temperature. Observations of fracture surfaces and measurements of hardness and residual stress distributions were carried out to investigate the fracture mechanism and fatigue strength. It was revealed that treating process sequence did affect residual stress distributions. Compressive residual stress generated at the surface of FPB treated specimen after nitriding was higher than that of the one FPB treated before nitriding. It was clarified that the higher the specimen hardness was, the higher compressive residual stress was generated at the surface. Therefore, FPB treatment after nitriding increased the fatigue strength of steel.

Tribological properties of structural steel modified by fine particle bombardment (FPB) and diamond-like carbon hybrid surface treatment

To improve the poor adhesion of diamond-like carbon (DLC) coatings to steel substrates, we have proposed a hybrid surface treatment, which is a combination of fine particle bombardment (FPB) and DLC coating. Specimens were treated by FPB using Cr shot particles prior to coating with DLC by the ionizing deposition method. Specimens with only the DLC coating without the FPB treatment (single-treated) were also prepared. The FPB treatment increased substrate hardness and roughness. In addition, a Cr-rich layer was formed on the surface because of the mechanical mixing of Cr shot particles into steel substrate. Reciprocating sliding wear tests were conducted to investigate the coefficient of friction. While the single-treated specimens showed a sudden increase in the friction coefficient resulting from delamination of the DLC coating, the hybrid-treated specimens maintained a low friction coefficient during wear tests indicating strong adhesion of the DLC coating. The reasons for good adhesion of the hybrid-treated specimens were investigated in terms of surface hardness and Cr enrichment. The relationship between substrate hardness and friction coefficient was investigated by preparing substrates with different hardness values. The results indicated that an increase in hardness is effective in suppressing of DLC coatings delamination, whereas a significant increase in hardness was not achieved by the FPB treatment. A roughened substrate without the Cr-rich layer was also prepared to examine the effects of substrate roughness and the presence of Cr. The results imply that strong adhesion of the DLC coating of the hybrid-treated specimens was due to the presence of Cr, which suppressed the delamination of the DLC coatings.

Effect of Fine Particle Bombardment Treatment on Tribological Properties and Adhesion of DLC Film Coated on SCM440 Steel

To improve poor adhesion of Diamond-like Carbon (DLC) coatings on the steel substrate, Fine Particle Bombardment (FPB) using Cr based shot particles are combined with DLC coating process. The FPB treatment distributes diffused Cr elements onto the treated surface, creating a Cr-rich layer. The FPB treatment increases the surface hardness and roughness. Wear test was conducted to compare the tribological properties of the DLC coated FPB treated steels and that of the DLC coated non FPB treated ones with a special focused on the Cr-rich layer, surface hardness and roughness. The DLC coated surface, after FPB treatment, kept low friction coefficient, while the DLC coated non FPB treated ones showed a sudden increase indicating the delamination of DLC layer. This is because of Cr-rich layer, which increase adhesion between DLC coating and steel substrate.

Effect of Compound-Layer Elimination and Introducing Compressive Residual Stress by FPB Treatment on Fatigue Properties of Plasma-Carburized Ti-6Al-4V Alloy

The effect of a duplex surface modification on the fatigue properties of Ti-6Al-4V alloy was examined. This method was composed of plasma carburizing and fine particle bombarding (FPB) treatment. Plasma carburizing at the first stage was conducted to form a hardened layer due to the diffusion of carbon. FPB treatment at the next stage was aimed for eliminating the brittle compound layer which was formed at the outermost surface and introducing compressive residual stress. In the case of the material plasma-carburized for 14.4ks at 1123K, cracks were initiated from the compound layer at relatively low stress amplitude level, so that the fatigue strength was greatly reduced. When the plasma-carburized material was further FPB-treated using SiC particles and high hardness steel particles, the compound layer was completely eliminated and compressive residual stress was introduced. As a result, the initiation sites of fatigue cracks were moved to the inside of the material just under the hardened layer and the fatigue strength was recovered to about the fatigue strength level of the untreated alloy. The above results showed that the duplex surface modification method examined in this study was effective to form the hardened layer which can improve the wear resistance without the great reduction in the fatigue strength of Ti-6Al-4V alloy.

Effect of Fine Particle Bombarding Process on Tooth Surface Properties and Tooth Surface Strength of Carburized Gears (1st Report, Effect on Tooth Surface Properties)

Fine particle bombarding (denoted as FPB) is one of the surface modification processes that makes fine (20-200μm in diameter) and hard (Hv 750-1000) particles impact with the metal surface at a high speed (more than 100 m/s), which is similar to shot peening. Although FPB has been already applied to extend lifetimes of a die and a metal cutting tool, and to reduce friction on the contact surface, the influence on the tooth surface strength of gears has not been clarified. The purpose of this study is to determine quantitatively the effect of FPB on the tooth surface strength of carburized gears and to clarify the factors caused by FPB that influence on the tooth surface strength. First, the author examined the tooth surface properties such as residual stress, roughness, hardness, surface texture, etc. using test gears processed by the FPB under three different conditions of arc height. A test gear performed by conventional impeller-type shot-peening was also used for comparison with the FPB. Next, durability tests were carried out using the gears to measure the tooth surface strength. The results showed that the FPB is effective to increase the tooth surface strength compared to conventional shot-peening. In the 1st report, the effect of the FPB on the tooth surface properties is described.

1012 マイクロディンプルによるメゾアンカー効果を用いたDLC被膜の摩擦係数制御(表面改質による機械の高性能化)

In recent years, DLC(Diamond Like Carbon) coating, which is well known for its high hardness and excellent ware resistance, has been widely used in several kinds of industries. However, in general, it is not easy to control the friction coefficient of DLC coating. So, in order to apply DLC coating for more machines and equipments, it is important to clarify the method of controlling friction coefficient of DLC coating more easily. So, in this study, DLC coating was performed on the surface of substrate which was formed micro-dimples by using Fine Particle Bombardment(FPB). Three types of coated specimens with different surface roughness were prepared and wear tests were carried out. The coated specimens which was formed micro-dimples indicated stable friction coefficient for long distance significantly. Furthermore, it is possible to control the friction coefficient of DLC coating easily by changing the surface roughness of substrate; the rougher the surface roughness, the higher the friction coefficient.

Effect of Fine Particle Bombarding Process on Tooth Surface Properties and Tooth Surface Strength of Carburized Gears (2nd Report, Effect on Tooth Surface Strength and Influencing Factors)

Recently the application of fine particle bombarding process (denoted as FPB) has been getting wider because of its superior effects compared to conventional shot-peening ; however, the influence on the tooth surface strength of gears has not been clarified. The purpose of this study is to determine quantitatively the effect of FPB on the tooth surface strength of carburized gears and to clarify the factors influencing on the tooth surface strength. First, the author examined the tooth surface properties such as residual stress, roughness, hardness, surface texture, etc. using test gears processed by the FPB under three different conditions of arc height. A test gear performed by conventional impeller-type shot-peening was also used for comparison with the FPB. These results have been described in the 1st report. Next, durability tests were carried out using the gears to measure the tooth surface strength. The results showed that the FPB is effective to increase the tooth surface strength by 1.21 to 1.28 times in Hertzian stress compared to conventional impeller-type shot-peening. Then, the following factors caused by the FPB that influence on the tooth surface strength increase were discussed. (1) Produced high residual compressive stress, (2) Increased hardness, (3) Good conformability on the tooth surface, (4) Micro hollows on the tooth surface generated during running. It was found that the latter two are unique factors caused by the FPB process. In the 2nd report, the effect of the FPB on the tooth surface strength is described.