Fine Particle Bombardment Treatment Research Articles

Effects of Particle Collision Treatments on Fatigue Strength of Ti–6Al–4V Alloy with Polishing Marks

In this study, we attempted to nullify the harmful influences of processing marks on the fatigue strength of Ti–6Al–4V alloy by particle collision treatments. As the surface treatments, fine particle bombarding (FPB) and shot peening (SP) were applied to form hardened layers and introduce compressive residual stress. The surface of the objective material was polished to a mirror surface to eliminate the influences of machining on specimens and was then grinded with emery papers (#80) to make uniform processing marks. After the particle collision treatments, the surface conditions, hardness distributions and residual stress were systematically examined, and their relationships with the fatigue strength were considered in detail. On observation of the surfaces, the processing marks were eliminated by the particle collision treatments. At the same time, the surface hardness was increased and high compressive residual stress was introduced. As a result, the fatigue strength was markedly improved by the treatments beyond the level of the material with the processing marks without deterioration of the mechanical properties. The improvement rates of the fatigue strength were high, at 75% by FPB treatment and 58% by SP treatment.

Loosening Evaluation of Bolted Joints Modified by Fine Particle Bombardment under Transverse Cyclic Loading

ABSTRACTThe objective of this article is to evaluate the loosening behavior of bolted joints modified by fine particle bombardment (FPB) under transverse cyclic loading. FPB treatment was conducted to thread surfaces of both the bolt and the nut. Self-loosening experiments were then performed on the bolted joint with high, medium, and low preload using a fatigue testing machine. The test results show that fretting wear occurs at the thread surface under transverse cyclic loading, which leads to gradual self-loosening of bolted joints without the rotation of the nut. FPB treatment alleviates thread wear by increasing the surface hardness and reducing the friction coefficient between threads, thereby improving the anti-loosening ability of bolted joints. After FPB treatment, the bolted joints with a lower preload exhibited a greater relative improvement in anti-loosening ability than those at a higher preload.

The influence of fine particle bombarding treatment on microstructure

The influence of fine particle bombarding treatment on microstructure

Investigation on the scuffing resistance of ductile cast iron as affected by fine particle bombardment to produce surface hardened layer and micro-dimpled surface

The objective of this paper is to investigate the influence of fine particle bombardment (FPB) on the scuffing behavior of ductile cast iron. Ductile cast iron samples were processed by FPB treatment, in which three injection air pressures (0.2MPa, 0.4MPa and 0.6MPa) were used for given particle flux (8–10g/s), treatment time (15s), nozzle diameter (9mm) and standoff distance (100mm). Surface morphology, microstructure and hardness of these samples were examined. Step–loading scuffing tests were then performed on a block-on-ring machine, in which the FPB treated ductile cast iron was used for the block and an alloy cast iron without FPB treatment was used for the ring. The test results show that FPB treatment improves the surface hardness of ductile cast iron by nanocrystallization. An increment of injection air pressure would increase the surface hardness through reducing the grain size within the nanocrystalline layer. FPB treatment decreases the friction coefficient through reducing the surface roughness and producing a micro–dimpled surface. The friction coefficient is decreased when increasing the injection air pressure. The scuffing resistance of ductile cast iron depends on surface hardness and friction coefficient; it would be improved through using a higher injection air pressure during the FPB treatment.

Influence of a hybrid treatment consisting of fine particle bombardment and powder impact plating on the scuffing behavior of ductile cast iron

The objective of this research was to determine the influence of applying a hybrid treatment, consisting of fine particle bombardment (FPB) and powder impact plating (PIP), on the scuffing behavior of ductile cast iron. Ductile cast iron samples were processed by an FPB treatment, a PIP treatment, and a hybrid treatment of both FPB and PIP. Scuffing behavior of these samples was investigated using block-on-ring tests. A piston alloy of ductile cast iron was used for the block and a cast iron cylinder alloy was used for the ring. Results showed that scuffing resistance depends on surface hardness and friction coefficient for the test samples. FPB treatment of block samples increases their surface hardness by nanocrystallization and reduces the friction coefficient of the tribological pair by reducing the surface roughness and producing a micro-dimpled surface. Thus, the scuffing resistance of FPB treated block is improved. The scuffing resistance is also improved by PIP treatment, which reduces the friction coefficient by producing a soft Sn film on the contact surface. After a hybrid treatment of both FPB and PIP, the surface hardness of the ductile cast iron substrate is increased and the friction coefficient of the tribological pair is further reduced relative to either single treatment. Therefore, hybrid treatments such as the ones described here can improve the scuffing resistance of cast irons.

Scuffing Behavior of Al-Si Alloy Modified by Fine Particle Bombarding and Powder Impact Plating Hybrid Surface Treatment

ABSTRACTThe occurrence of scuffing is widely observed on tribological components made of Al-Si alloys. The object of this study is to investigate the scuffing behavior of Al-Si alloy modified by fine particle bombarding (FPB) and powder impact plating (PIP) hybrid surface treatment. FPB treatment, PIP treatment, and hybrid treatment consisting of FPB and PIP were conducted on Al-Si alloy samples. The surface morphology, microstructure, and hardness of the samples were examined. Block-on-ring tests were performed to investigate the scuffing resistance of the samples. The test results show that the scuffing resistance of Al-Si alloy depends on the surface hardness and friction coefficient. Scuffing resistance is improved by FPB treatment, which increases the surface hardness by nanocrystallization and reduces the friction coefficient by decreasing the surface roughness and producing a microdimpled surface. PIP treatment reduces the friction coefficient by generating an Sn coating on the surface of the sample, thereby improving the scuffing resistance. After FPB and PIP hybrid surface treatment, the surface hardness is increased and the friction coefficient is further reduced. Therefore, the sample modified by hybrid surface treatment exhibits the highest scuffing resistance.

微粒子衝突処理により形成された表面近傍の微視組織評価

In this study, fine particle bombarding treatment (FPB) was applied to A5052 aluminum alloy, the effects of FPB treatment time (5, 10, 20, 40s) on the near-surface microstructure hardness, and fatigue strength was examined. The near-surface microstructure of 20s and 40s FPBed Al-Alloy was nano-crystallized, and lamellar structures were partially formed. The average grain sizes in and around lamellar structure are 65nm and 125nm by TEM observation. The relationship between hardness and grain size indicates Hall-Petch relationship. Moreover, fatigue tests were carried out with cantilever-type rotary bending fatigue test machine. Fatigue strength of 20s-FPBed Al Alloy is highest, the relationship between fatigue strength and grain size indicates linearity. Then 20s-FPBed A5052 had the fatigue strength equivalent to 7000 series aluminum alloys.

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%.

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%.

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 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 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 Fine Particle Bombarding Treatment Conditions on Surface Origination of Materials

In this study, we analyzed effect of fine particle bombarding (FPB) treatment conditions on structural transformation close to the material surface and also measured temperature close to the material surface in FPB treatment. As a result, when an intensive condition was used in FPB treatment, a lamellar structure was observed. In other words, dents and bumps are formed in the initial stage of particle collisions on the material surface. Repeatedly processed, the protruded portions are supposed to be then bent over, resulting in an atomized structure. On the other hand, we measured temperature close to the material surface to find temperature rising up to about 600. In addition, when the fine particle collided continuously to the same portion, the specimen reached a melting state. These results indicate that heat generated in FPB treatment has a drastic effect on structural transformation close to the material surface.

EFFECT OF FINE PARTICLE BOMBARDMENT TEMPERATURE ON THE SURFACE CHARACTERISTICS OF Ti-6Al-4V ALLOY

In this study, we performed Fine Particle Bombardment (FPB) treatment on Ti -6 Al -4 V alloy surfaces at room temperature, high temperature and low temperature. Treated surface were characterized with surface microstructure, hardness and diffusion phenomena. Diffusion was slightly accelerated in higher temperature and inhibited in lower temperature compared to the room temperature. These phenomena agree with the physical laws of diffusion. Hardness increased extremely in the higher temperature treated specimen. This result suggests that higher temperature treatment improves mechanical properties of the substrate surface. Consequently, processing temperature greatly affects mechanical properties of treated surface and diffusion phenomena induced in the FPB treatment.