Sandblasting Research Articles

A review on surface treatment of titanium implant

Dental implants are fixtures that serve as replacements for the root of the missing natural tooth and in the current day dental practice. Success or failure of the dental implant treatment is mainly based on the principles of osseointegration, which is the direct and stable anchorage of an implant due to the formation of bony tissue around the implant. A number of systemic and local factors influence the production of an osseointegrated interface and therefore the stability of the implant. Present article covers various methods used for surface treatment of titanium and titanium alloy implants. They are mechanical method such asMachining,Grinding,Polishing and Grit blasting. Chemical treatment include Acid treatment,Hydrogen peroxide treatment,Alkali treatment.Sol–gel coatings include TiO2 coating,Calcium phosphate coatings, Titania/hydroxyapatite composite coatings and Silica coating.Electrochemical treatments includes Thermal spraying,Plasma spraying.Ion implantation and deposition include Oxygen implantation, Nitrogen implantation,Carbon implantation and deposition, Metal ion implantation. Surface modification methods used to improve the mechanical, chemical and biological properties of titanium and its alloys for biomedical application. Keywords: Surface treatment, Osseointegration, Biomaterials, Microtopography, Biocompatibility.

Influence of surface and subsurface properties on the bonding between yttria stabilized tetragonal zirconia polycrystals and a veneering ceramic

Since the late 90s the use of zirconia in dentistry increases, it is used for example for all-ceramic restorations, brackets and implants. This article will deal with all-ceramic restorations. For the production of these restorations many manufacturing steps are necessary: Pre-sintering of the ceramic powder, soft machining (pre-sintered condition), sintering and a pre-processing of the ‘finished’ geometry like hard machining (fully sintered) or grit blasting (GB) in combination with a final staining or veneering step. Most of the steps (excluding soft machining in a pre-sintered condition and sintering) are still carried out manually. All these techniques are associated with the production of flaws in different scales, in conjunction with thermal and residual stresses and phase transformations. This study investigates how those surface and subsurface properties, which arise due to the manufacturing process, influence the bonding between a framework ceramic and a veneering ceramic. This will be investigated by means of a scratch test.

Study on the Influence of the Main Parameters of Pellets Distribution and Settlement in the Passage of Shot Blasting

Study on the Influence of the Main Parameters of Pellets Distribution and Settlement in the Passage of Shot Blasting

Investigation of the deformation and strength properties of fouled graded macadam materials in heavy-haul railway subgrade beds

Over the course of long-term operation, the graded macadam materials used in heavy-haul railway subgrade bed surfaces become polluted to different degrees. This fouling is due to its own breakage, the intrusion of external coal debris, sand blasting, dust, and other foreign materials that accumulate on the ballast along with rainwater seepage, and the internal-structure mud-pumping. This study had the goal of determining the variation law for the deformation and strength characteristics of fouled graded macadam materials under cyclic loading. First, graded macadam materials with different fine particle contents were prepared, and a series of dynamic triaxial tests were carried out using a GCTS large-scale cyclic triaxial test system. These initial tests were conducted to determine the mechanism for the coupled effect of the fine particle content, confining pressure, and dynamic stress amplitude on a specimen’s accumulative plastic strain under cyclic loading. Using the plastic stability theory as a guideline, the dynamic deformation behaviours of specimens under different stress levels were determined, and a critical dynamic stress calculation model for specimens in the plastic creep state was established by considering the parameters of the confining pressure and fine particle content. Then, an accumulative plastic strain prediction model was established for specimens in the plastic creep state considering the stress level and fine particle content parameters, and a hardening index calculation model under cyclic loading was also established. At the same time, the physical significance of each parameter was clarified. Finally, a dynamic stress-strain relationship calculation model for fouled, graded macadam materials, which took into account the stiffness hardening under cyclic loading and stiffness degradation after fine particle intrusion, was constructed on the basis of a modified version of Iwan’s series–parallel model. The research results provide a reference for evaluating the health of existing heavy-haul railway subgrades and will be useful for designing new subgrade structures that take into account the comprehensive control principle of strength and deformation.

Surface roughness prediction and parametric optimization of shot blasting of Al7068 using RSM

The mechanical based shot blasting was used to remove the oxides and scales from the surface of the materials. It was used to enhance the surface properties. In this work, aluminium 7068 alloy was involved in the shot blasting process. The particle velocity, standoff distance (SOD) and impact angles were included as input factors. These factors were mainly affects the Surface Roughness (SR). The round steel balls with diameter with 2 mm diameter were used for the shot blasting process. In addition to that, the elliptic and square shape of glass beads particles were used to enhance the surface finish. The parametric effect and surface roughness optimization was achieved through Response Surface Methodology (RSM). The role of factors has been analyzed through the variance test.

Effect of various porcelain surface treatment methods on shear bond strength of orthodontic adhesive

Objective: to evaluate the effect of different treatment methods of porcelain surfaces before bonding on the shear bond strength of orthodontic adhesive. Material and methods: This study was conducted on a sample of sixty feldspathic porcelain cylinders stored in artificial saliva for a week. The sample was divided into five equal groups twelve each according to the applied surface treatment, Gp1 diamond bur roughening, and Gp2 etching 37% phosphoric acid GP3 Laser etching Gp4 9% hydrofluoric acid etching Gp5 sandblasting 50 micron aluminum oxide particles. Randomly one specimen from each group was scanned by electron microscope while the other specimens were bonded to metal brackets and stored in artificial saliva for one week then mounted in acrylic blocks to allow measuring the shear bond strength using Instron universal testing machine. Results: Diamond bur group showed significant difference with all other groups. There is significant difference between phosphoric acid and laser on one hand and sand blasting and hydrofluoric on the other hand. But for both phosphoric acid and laser groups there is no significant difference and for both sand blasting and hydrofluoric acid groups there is no significant difference. Conclusion: The diamond bur group showed the highest bond strength, while phosphoric acid showed the least one.

Fatigue performance of Q355B steel substrate treated by grit blasting with and without subsequent cold spraying with Al and Cu

Grit blasting and cold spraying are widely used as surface modification processes to improve the performance of steel substrates. In this study, 80-mesh grits were optimized for grit blasting through a bonding quality evaluation of cold-sprayed Al and Cu coatings on Q3555 steel substrate blocks. Fatigue testing was conducted on Q355B steel specimens treated by grit blasting with and without subsequent cold spraying with Al and Cu to study the fatigue behavior of the treated substrates. The results show that grit blasting with and without subsequent cold spraying can increase the crack length and decrease the crack growth rate, thereby prolonging the fatigue life of Q355B steel substrate, and that grit blasting with subsequent cold spraying with Cu achieves a greater improvement effect than cold spraying with Al. Finally, scanning electron microscopy (SEM) was performed on the fatigue fractures to examine the mechanism by which the fatigue life is prolonged by grit blasting and cold spraying.

Effect of Grit Blasting Parameters on Surface and Near-Surface Properties of Different Metal Alloys

In thermal spray, grit blasting is the standard method used to prepare the substrate surface before coating deposition. This study examines the effect of the grit blasting parameters on the residual stresses, roughness and hardness of three metal alloys with widely different mechanical properties: low-carbon steel, Ti-6Al-4V and Inconel 718. It also estimates the density of dislocations using the Williamson–Hall method. The dislocation structures of low-carbon steel grit blasted at different grit impingement angles were observed under a transmission electron microscope. The surface dislocation density was found to increase with the blasting time and angle of impact. Moreover, the depth profile of the dislocation density was in good agreement with that of the hardness profile of the blasted specimen. The residual stress depth profiles of each material at different blasting pressure showed an increase in the value and depth of maximum compressive residual stresses. Both surface residual stresses and roughness were found to increase with the grit blasting pressure, angle and, to some extent, with time and stand-off distance. The mechanisms of material erosion were found to be microcutting and indentation at lower and higher angles of abrasive impingement, respectively. The extent of damage of the materials was explained on the basis of the Johnson–Cook flow strength model.

Surface Activated Bonding of Glass Using Aluminum Oxide Intermediate Layer for Microchannel Fabrication

With a huge demand from the society on a more precise and rapid biological molecule detection in a reduced amount of biosamples, biomedical engineering technology has been in rapid development, resulting in a wide range of biosensors using microfluidic systems. For microfluidic structure, glass is still the main material owing to its chemical stability, cost efficiency, and optical characteristics. In order to seal the fluidic channel based on glass materials, glass substrates should be bonded to cover the channel grooves. Conventionally, glass materials are bonded by anodic bonding or hydrophilic bonding at high temperature process, in which the bonding surfaces are bonded via covalent bonds. However, these bondings of glass at high temperature lead to residual stress at the bonding interface and damage to the device on the substrate, especially the biomolecule sensors using enzymes. In addition to the process temperature, the bonding interface should be transparent as a wide range of biosensors utilizes optical measurements to detect biomarkers.For this reason, a room temperature bonding of glass is desirable for the microchannel sealing. As a room temperature direct bonding method of glass, modified surface activated bonding (mSAB) using Si intermediate layer has been reported to achieve a strong bond of glass via Si layers and Fe nano adhesion layers [1]. Although this approach enables the glass bonding at room temperature, the bonding interface is covered with the deposited Si layers, resulting in deteriorated optical characteristics at the bonding interface. Therefore, mSAB using Si intermediate layer is not suitable for the optical measurement of biomolecules in the microchannels.Recently, we reported a new SAB using aluminum oxide (AlO) intermediate layer instead of Si [2]. AlO has excellent optical characteristics such as low absorbance and refraction index uniformity. From the aspect of bonding, thin AlO membrane by ALD has been reported as intermediate layer for hydrophilic bonding [3]. Furthermore, it has been also reported that bulk sapphire is bonded by standard SAB process, where the sapphire surfaces are activated by Ar ion beam irradiation and bonded through amorphous-like AlO structure [4].In this study, we apply mSAB using AlO intermediate layer for glass substrate and Si substrate with microchannel patterning. The bonding is evaluated from the perspective of the channel sealing.In order to evaluate the sealing by the proposed bonding method, microfluidic channels were realized on a 4 inch and 525 µm thick Si wafer. The patterning consists of 64x64 inlet ports 100 µm diameter, 46-142 µm wide microchannels, 4x4 mm2 cavity, and capillary pump. For the fabrication of the microfluidic components, inductively coupled plasma reactive ion etching (ICP-RIE) was employed. For the sealing of the microchannels on the Si wafer, mSAB using AlO intermediate layer was conducted. The substrates are activated by Ar ion beam and the AlO layers are deposited by ion beam sputtering, followed by contact and press. After sealing by the wafer bonding, through-glass holes were fabricated by sand blast etching to enable flow in the channels.In order to evaluate the sealing of the microfluidic system by the proposed bonding method, first, scanning acoustic tomography (SAT) was conducted. As shown in Figure, the whole structure is sealed without significant voids.Additionally, we also evaluated the sealing of the microfluidic structure by a flow test. A droplet of phosphate buffered-saline (PBS) as a model liquid of biosample was put on the inlet ports. As a result, PBS flow was observed through the microchannels and capillary pump without leakage. Therefore, it can be said that the proposed bonding method successfully sealed the microfluidic system and the bonding interface kept its transparency.From these result, it is indicated that the developed bonding method is suitable for the microchannel device fabrication by realizing a transparent bonding interface at room temperature. MMR Howlader, S. Suehara, and T. Suga. Sensors and Actuators A: Physical, 127(1):31–36, 2006.Takeuchi, F. Mu, Y. Matsumoto and T. Suga, 6th International Workshop on Low Temperature Bonding for 3D Integration (LTB-3D), Kanazawa, Japan, 2019, pp. 85-85.Ikku, M. Yokoyama, R. Iida, M. Sugiyama, Y. Nakano, M. Takenaka, and S. Takagi, 23rd International Conference on Indium Phosphide and Related Materials, May 2011, pp. 1–4.Takagi, Y. Kurashima, A. Takamizawa, T. Ikegami, and S. Yanagimachi, Jpn. J. Appl. Phys., Vol. 57, 02BA04, 2017. Figure 1

Energy Absorption and Deformation Behavior of 3D Printed Triply Periodic Minimal Surface Stainless Steel Cellular Structures under Compression

This article investigates the energy absorption performance and deformation mechanism of 316L stainless steel (SS316L) triply periodic minimal surface (TPMS) cellular structures fabricated by a selective laser melting (SLM) technique. The as‐built specimens are subjected to abrasive blasting treatment to improve the surface quality of the printed parts, in order to reveal the true surface and mechanical characteristics of the TPMS structures. It is found that the P‐type structure outperforms the G‐type structure with a higher energy absorption capability at low relative densities (<0.35). The macroscopic examination of these micro‐architectures reveals that the P‐type structure develops a rapid local cell deformation following the diagonal shear geometry on the face sheet, whereas the G‐type structure experiences continuous strain hardening along the stress plateau and deforms in a gradual manner during compression. The apparent strain hardening effect of the G‐type structure is caused by the development of many macro‐localities with extreme geometry distortion and cell wall self‐contacting during compression. The findings in this study may provide valuable insight into design, fabrication, and post‐fabrication treatment of metallic TPMS structures for the applications of high compression performance.

Mechanical and Crack-Sensing Capabilities of Mode-I Joints with Carbon-Nanotube-Reinforced Adhesive Films under Hydrothermal Aging Conditions.

The fracture behavior and crack sensing of mode-I joints with carbon nanotube (CNT)-reinforced adhesive films were explored in this paper under hydrothermal aging conditions. The measured fracture energy of CNT-reinforced joints in grit blasting conditions is higher for non-aged samples than for neat adhesive joints (around 20%) due to the nanofiller toughening and crack bridging effects. However, in the case of brushed surface-treated adherents, a drastic decrease is observed with the addition of CNTs (around 70%) due to the enhanced tribological properties of the nanofillers. Hydrothermal aging has a greater effect in the CNT-reinforced samples, showing a more prevalent plasticization effect, which is confirmed by the R-curves of the specimens. The effects of surface treatment on the crack propagation properties was observed by electrical resistance monitoring, where brushed samples showed a more unstable electrical response, explained by more unstable crack propagation and reflected by sharp increases of the electrical resistance. Aged specimens showed a very uniform increase of electrical resistance due to slower crack propagation, as induced by the plasticization effect of water. Therefore, the proposed adhesive shows a high applicability for crack detection and propagation without decreasing the mechanical properties.

Estimation of depth and degree of mill roll surface hardening during grit texturing

The paper presents shot blasting (SB) as the most common method of arrangement of temper mills rolls surface microgeometry, providing required roughness of the cold-rolled strip. The surface riffing studies were carried out at the Willibrator industrial unit; metallographic studies were performed using MEIJI 2700 optical microscope and JSM-6490LV scanning electron microscope. Refinement of the surface layer structure during interaction of the roll material with the grit was revealed. In the work the lower bound method, one of the methods of plasticity theory, is used for theoretical analysis of the SB process. To make computations easier, the roll microcave is approximated to spherical shape. Quantitative estimates of deformation degree and the depth of hardened layer were determined by speed of the grit and hardness of the roll surface. The depth of hardened layer is obtained by the size of used grit, and to a lesser extent, by the speed of grit impact on the roll surface and textured surface hardness. It has been searched out in literature that increase in hardness by one unit leads in average to 3 % increase in resistance. Thus, SB application allows reduction of time of rolls rehandling of temper mills by 6.0 – 10.5 %, depending on application modes of rolls riffing with grit. Analysis of microstructure have shown that increase in hardness of the surface layer is a consequence of refinement of its structure in process of interaction with the grit. It has been revealed that increase in hardness of the surface layer leads to an increase in its wear resistance and fatigue strength. The authors of the work have found that at speed of 60 m/s the hardness increases by 3.5 units.

Performance and failure assessment of adhesively bonded non-crimp fabric carbon fiber/epoxy composite single lap joints

Carbon fiber-reinforced plastic (CFRP) composite materials have experienced increased use for load-bearing structures in automobiles owing to their high specific mechanical properties. However, critical to widespread adoption of CFRPs are the development of robust joining methods with appropriate surface preparation to maximize joint strength, as well as an improved understanding of failure mechanisms to enable computational modeling for supporting design. In the present study, an adhesively bonded non-crimp fabric CFRP single lap joint (SLJ) was investigated to quantify the effect of the composite adherend surface treatment and stacking sequence on the lap shear strength, and to assess the corresponding failure mechanisms. Single lap shear test results revealed that the highest lap shear strength was achieved by abrading the surface with sandpaper, relative to an unprepared surface or one treated by grit blasting. Similarly, an adherend with a higher effective flexural longitudinal modulus, achieved through stacking sequence, increased the lap shear strength owing to reduced Mode I loading on the adhesive joint. Distinct failure processes were observed for CFRP adherends with different stacking sequences, where the locations of intra-ply and inter-ply cracks varied as a result of variations in the in-plane and out-of-plane stresses. Notwithstanding, the final failure event for all SLJ specimens was failure of the thin layer of matrix in the 0° ply of the adherends. Three-dimensional finite element analyses of the SLJ specimens were employed to determine the local stress components driving the observed failure mechanisms within the plies of the CFRP adherends. The results of this study provide a recommended surface treatment to maximize adhesive joint strength for CFRP adherends, along with a comprehensive assessment of failure mechanisms, to inform the design and application of CFRP materials in lightweight structures.

Crack sensing mechanisms of Mode-II and skin-stringer joints between dissimilar materials by using carbon nanotubes

The mechanical and crack sensing capabilities of CFRP-metal Mode-II coupons and skin-stringer T-joints under bending conditions with carbon nanotube (CNT) doped adhesive films are explored. Different surface treatments of the aluminium substrate are tested (grit blasting and sandpaper brushing). Mode-II energy fracture slightly increases with CNT addition due to the nanoparticle toughening effect when the surface treatment is adequate. However, in the case of brushed specimens, the enhanced lubricant properties of CNTs leads to the promotion of weak interfaces between adhesive and metal substrate. The electrical resistance increases with the load nose displacement with a good correspondence to the crack length. A crack opening effect is herein noticed in the last stages of the Mode-II tests due to the difference between the stiffness of metal and CFRP adherents, which is reflected in a sudden increase of the electrical resistance. These results have been also validated by theoretical analysis. Electromechanical response of T-joints shows a similar behaviour with an increasing sensitivity when placing a CFRP stringer, due to a more prevalent crack opening observed in this type of specimens. Therefore, crack sensing capabilities are demonstrated at both coupon and sub-element level.

Optimal sampling plan for an unreliable multistage production system subject to competing and propagating random shifts

Sampling plans play an important role in monitoring production systems and reducing quality- and maintenance-related costs. Existing sampling plans usually focus on one assignable cause. However, multiple assignable causes may occur, especially for a multistage production system, and the resulting process shift may propagate downstream. This article addresses the problem of finding the optimal sampling plan for an unreliable multistage production system subject to competing and propagating random quality shifts. In particular, a serial production system with two unreliable machines that produce a product at a fixed production rate is studied. It is assumed that both machines are subject to random quality shifts with increased nonconforming rates and can suddenly fail with increasing failure rates. A sampling plan is implemented at the end of the production line to determine whether the system has shifted or not. If a process shift is detected, a necessary maintenance action will be initiated. The optimal sample size, sampling interval, and acceptance threshold are determined by minimizing the long-run cost rate subject to the constraints on average time to signal a true alarm, effective production rate, and system availability. A numerical example on an automatic shot blasting and painting system is provided to illustrate the application of the proposed sampling plan and the effects of key parameters and system constraints on the optimal sampling plan. Moreover, the proposed model shows better performance for various cases than an alternative model that ignores shift propagation.

Influence of the laser ablation surface pre-treatment over the ageing resistance of metallic adhesively bonded joints

In order to prevent the generation of a potential weakness at the substrate/adhesive interface of adhesively bonded joints, many methods were developed during the decades to pre-treat the substrates surfaces before the deposition of the adhesive. Experimental tests were carried out to simulate the real environmental conditions in which the joints have to work characterizing the mechanical properties of the joints caused by the exposition to high temperature, moisture, presence of chemical agents. The industrial need towards long-scale problem lead to the development of specific accelerated ageing methods able to induce in few weeks the same damage mechanisms within the joints which arise in years during their working life. In this work, different surface laser pre-treatments were studied with a focus on the influence that pre-treatments produce over the variation of the tensile failure load of Single Lap Joints (SLJ), previously subjected to different accelerated ageing cycles. Simple degreasing and grit blasting were also considered as reference treatments. The materials chosen for the manufacturing of the substrates were an aluminium alloy (AA 6082-T6) and a stainless steel (AISI 304). Three different accelerated ageing techniques were tested and compared to each other: (i) a cycle involving the simultaneous presence of high temperature gradient and moisture (method A), (ii) the immersion into an alkaline foam-forming cleanser (method B), and (iii) the immersion into an acid foam-forming cleanser (method C). The results showed that, while the method A did not significantly modify the mechanical strength of the joints, the method B and C resulted detrimental for the mechanical performance of the joints, even if their sensitivity to the tested pre-treatments was different. In particular, for both aluminum and stainless steel joints, it was noticed that the laser pre-treatment was able to reduce the loss of strength produced by the ageing process in comparison with the two reference pre-treatments. However, this result was also dependent of the specific value of energy density used for the laser ablation during the joints pre-treatment.

Chemical surface finishing of electron beam melted Ti6Al4V using HF-HNO3 solutions

Electron Beam Melting is an Additive Manufacturing technology that allows the production of items using metal powder as raw material. The main advantage of Additive Manufacturing (AM) is realizing complex shape components; however one of the main defects is the poor quality of the surface. To this aim, different post processing treatments have been proposed such as machining, surface laser melting, sand blasting, etc.

Influence of Grit Blasting on Residual Stress Depth Profile and Dislocation Density in Different Metallic Substrates

This work deals with the effect of grit blasting on the surface and in-depth properties of a number of commercially available metals/alloys, i.e., low carbon steel, C45 steel, SS316, Ti-6Al-4V, Inconel 718, and Hastelloy X. The residual stress depth profile and dislocation density of the specimens were determined using X-ray diffraction. A substantial increase in dislocation density was observed after grit blasting. A transmission electron microscope was utilized to observe the dislocation structure in a grit-blasted specimen. Strain hardening was also observed at the blasted surface owing to dislocation interaction and entanglement. The hardness profile followed a trend similar to that of dislocation density along the depth of grit-blasted low carbon steel. Moreover, compressive residual stress is induced in the blasted surface having a maximum value at a certain depth. The maximum induced compressive residual stress was found to have a good correlation with the Johnson–Cook flow stress. Moreover, the depth of the affected layer and the increase in hardness were found to depend on the yield strength and the strain hardening exponent of the materials, respectively. A plastic deformation-induced phase transformation from austenite to martensite was also identified in the case of SS316.

THE ANTI-CORROSIVE REPAIR METHODS FOR DEGRADED WEATHERING STEEL BRIDGES

The existing rust with heavy amounts of salinity or anti-freezing agents on the weathering steel bridge surface can lead to serious durability issues. In the event that the anticorrosion functions of weathering steel bridges do not perform satisfactorily, it is necessary to eliminate the cause or to consider the repair coating and the life extension process. In order to achieve the expected life of the repair coating, it is important to perform the correct surface treatment, appropriate surface preparation (near-white blast cleaning, ISO standard Sa2 1/2 equivalent), and the certain removal of rust containing salinity (50 mg/m2 or below). This study provides state-of-the-art techniques on repair method, which is two repair coating methods and one simple repair method for weathering steel bridges. In 2015, some repair methods, with considerable effectiveness, were carried out to actual weathering steel bridges with undesired rust generation. The investigation of three years after repair coating shows that both repair coating film is confirmed to exhibit good corrosion resistance. The weathering steel surface repaired by simple repair method is also in a good state.

Effects of Substrate Composition and Treatment Times on the Erosive Wear of Titanium Aluminide Coating: Prepared By Pack Cementation

This present work aims to investigate the effect of processing time on the erosion resistance of 316 stainless steel and AISI H13 hot working tool steel treated by pack cementation. For this purpose, aluminum and titanium elements were simultaneously deposited on the surface of the two steels at 1050 °C for 4, 8 and 12 h using a pack mix containing an NH4Cl-based activator. The erosion wear experiments were conducted using both air jet and sand blast erosion equipment at impact angles of 30° and 90°. The microstructures of the two studied steels, in terms of surface morphology and related formed phases, were investigated using X-ray diffraction, scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectroscope (EDS), while the hardness and the erosion resistance of the coatings were assessed using Vickers’ microhardness and the weight loss per unit mass erodent, respectively. The results showed that all coatings have high erosion rate values at low impact angle of 30° which is thought to be associated with ductile erosion behavior. Furthermore, the coatings obtained on 316 stainless steel exhibited better erosion resistance than those obtained on AISI H13 steel. SEM analysis of eroded surfaces of all coatings revealed that the predominant erosion mechanism of Ti–Al pack cementation coatings was the formation and extrusion of platelet.