In automotive industry, thermal spray process is used to reduce engine weight by replacing cast iron liners inserted in cylinder bores. Especially, twin wire arc spray is one of widely used thermal spray processes with inexpensive cost and high deposition rate. In this study, two kinds of wire materials, low carbon steel (0.07 wt.%C) and high carbon steel (0.80 wt.%C) were deposited by twin wire arc spray process using two kinds of process gas (i.e., compressed air and nitrogen) in order to elucidate effects of carbon contents of ferrous coating and process gas type on the hardness and wear resistance of coating. In case of hardness, low carbon steel coatings had higher hardness when air was used as process gas whereas high carbon steel coatings had higher hardness when nitrogen was used, which was caused by the counter effects of carbon loss and oxide formation. The results of sliding wear test in lubricated condition indicated that coatings with higher hardness have better wear resistance and oxides improve wear resistance by playing a role as solid lubricant. The main wear mechanism was splat delamination induced by inter-splat crack, and traces of other wear behaviours such as splat tip fracture and abrasive wear were also observed.

In this study, ball-milled Al 2 O 3 powder was used as a feedstock material for vacuum kinetic spray to deposit hard ceramic Al 2 O 3 coating on a relatively soft polycarbonate substrate. Microstructural and X-ray diffraction analysis of powders and coatings were performed. The results shows that the ball-milled powder has more unstable state than the primary powder. Compared to primary Al 2 O 3 coating the crystallite size and coating thickness of ball-milled Al 2 O 3 coating are smaller and thicker, respectively. Since the ball-milled Al 2 O 3 particles are more easily fragmented during the VKS coating process, it is possible to deposit hard Al 2 O 3 coating on the soft polycarbonate substrate.

In this study, arrested reactive milling (ARM) is used to prepare Al-Ni composite powder for deposition on copper liners via kinetic spraying. Among the main goals are to obtain a better understanding of how the milling process affects deposition efficiency and the reactivity of the coatings and to find a way to reduce the amount of remaining solid lubricant after milling. Al-Ni powders were produced under a wide range of conditions and heated to various temperatures to eliminate stearic acid. The powders were sprayed using fixed process parameters and deposition efficiencies, reactivities, and heat values were measured and are compared along with coating microstructures. The procedures used are described and the findings of the study are presented and discussed.

Mechanically mixed Al-Ni powders with different nickel fractions were deposited on Cu substrates by kinetic spraying. Deposition efficiency and porosity were measured and finite element analysis was used to model single and multiple particle impacts. Increasing the fraction of nickel in the feedstock powder reduced the porosity of the Al-Ni coatings but at the expense of deposition efficiency. The reason for this is explained based on particle velocity measurements and impact models. With that information, dense, well adhered coatings were produced by increasing the tamping effect of Ni, resulting in local melting of the Al at the Al-Ni interface.

Vacuum kinetic spray (VKS) technology was employed to fabricate AlN films. In order to investigate the relationship between the deposition behavior with change of the size and microstructure of feedstock, AlN powders were pre-treated through ball-milling and heat-treatment. It is observed that the particle size decreased and defect density increased after the ball-milling. After the heat-treatment of the ball-milled powder, on the other hand, the particle size was not changed significantly, while the defect density was reduced by recovery. The coatings of ball-milled and heat-treated powder were obviously thicker than that of only ball-milled powder. It is inferred that, during the heat-treatment, although the defects were reduced by recovery, the dislocations were aligned, through which the cracks were able to propagate more easily. By the combined effects of ball-milling and heat-treatment, more fragmentations with new surfaces of the particles were generated during VKS, which would improve the deposition efficiency. Therefore, in VKS process, the deposition behavior is shown to be affected by not only particle size, but also the defect density and microstructure of the feedstock powder.

Pure Al coatings were fabricated on Cu substrates via kinetic spraying for double-layered Cu liner. The coatings need to endure the high strain rate severe plastic deformation during explosion, in this study, the process optimization of Al deposition was initiated with a definition of “critical velocity” of Al particle in kinetic spraying on a basis of numerical modeling and computations using ABAQUS finite element codes. The simulation results revealed that the critical velocity of Al particle at room temperature (RT) was 780 m s -1 , and the critical velocity decreased as particle temperature increased. On the basis of simulation results, mechanical properties such as bond strength of the coatings formed under various process conditions were evaluated and compared. These properties were discussed in terms of the processing-structure-property relationships.

Vacuum kinetic spray (VKS) is a relatively new coating process by which dense, low porosity nanostructured ceramic coatings can be produced. Titanium nitride films with thickness of 0.5-5 µm on glass were fabricated by VKS method for a mechanism and microstructure study. Deposition behavior and structure with different gas consumption and gun traverse speed were studied based on X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM). The as-deposited titanium nitride film consisted of ~20 nm grains is well condensed and expected to have excellent mechanical properties.

The new kinetic spray coating technique, vacuum kinetic spray (aerosol deposition), utilizes the pressure gap between powder hopper and coating chamber which is vacuumed. In this study, to investigate the deposition mechanisms present in the vacuum kinetic spray coatings, α-Al 2 O 3 and glass were chosen as the powder and substrate materials, respectively, and these were considered as the reference materials to examine the effect of free surfaces after particle fractures. Based on the finite-element modeling (using an AUTODYN-2D 12.1), single particle impacts were simulated, and the results elucidated the material shape, temperature variation and mass change of particle due to its fracture during impact. The plots of total mass change as a function of particle impact velocity demonstrate the deposition-optimized velocity zone (DOVZ) for successful deposition. Compared to as-received powders, from the transmission electron microscope (TEM) images, the defects such as dislocations of the ball-milled powders might increase the tendency of the powder particles to fracture upon impact. The cross-section images of the coating showed that the particle sizes of the coating were drastically decreased compared to those of initial powders. During coating, fractured particles enlarged the thermodynamically unstable free surface area and have a tendency of formation of bonding.

Tiny circuit design reliability issue related to competitive signal was investigated in a sense amplifier (SA) circuitry of SRAM by E-Beam probing technique in this paper. The irregular output signals then traced back to former stage circuit and identified associated waveforms. With such design concept and technique tracing, the invisible and cunning circuit mismatch reliability issue could be revealed successfully.

This study compares the deposition behavior of kinetic sprayed bronze-diamond composite coatings produced using different mixtures of helium and nitrogen gas. To determine impact properties of the diamond particles, bare and nickel-coated diamonds are deposited on bronze layers and the effects of plastic deformation are examined using SEM and finite-element analysis. The results indicate that the deposition efficiency of diamond is determined by several factors and depends more on the angle and shape of the diamond particles than on the deformation properties of the bronze matrix.

This study assesses the effectiveness of nickel-coated diamond powder for producing metal-diamond composite coatings by cold spraying. The results of the investigation show that diamond fracturing was mitigated by the protective nickel coating. In general, the softer the metal matrix and the finer the diamond, the less fracturing that occurs and the greater the diamond fraction in the composite layer. It is also shown, however, that deposition efficiency and diamond fraction must be improved especially for diamond sizes of 50 μm and above.

In the present investigation, thermally enhanced kinetic spraying of titanium onto mild steel substrates is carried out in conjunction with powder preheating to obtain a dense coating using low-cost nitrogen as the process gas. Prior to this, a prototype model was developed for process optimization based on numerically approximated adhesion factors. The simulation results show that adiabatic shear instability accelerated by thermal energy and subsequent particle impact leads to the formation of an enhanced thermal boost-up zone that closely correlates with deposition behavior and coating properties. It is thus shown that the deposition efficiency of titanium can be more than 90% and porosity less than 1% when nitrogen gas is used for cold spraying.

This paper provides a summary of the status and potential of thermal spray activities in Korea. It describes how various market sectors in Korea are using spray coating technology and presents annual sales estimates and share of market data broken out by industry, spraying technology, and patents awarded. It also reviews recent advancements in the development and use of thermal spray technology in Korea along with anticipated future impacts.

This study assesses the potential of kinetic-spray coatings for dealing with the effects of soldering and erosion on aluminum casting dies. In the experiments, molybdenum-boride cermet and cobalt-based alloy powders are cold sprayed onto SKD61 substrates. Coating microstructure is assessed via SEM and XRD analysis and several mechanical properties are measured. In order to evaluate soldering resistance, the coatings are immersed in a molten aluminum bath. Although cold-sprayed CoCrNiWC exhibited high coating density and low porosity, its soldering resistance was significantly lower than that of MoB-NiCr. The boride cermet coating not only exhibited superior soldering resistance, but also higher hardness, bond strength, and wear resistance. However, its deposition efficiency needs further improvement.

In this study, Cu-based bulk metallic glass coatings were deposited by atmospheric plasma spraying with different hydrogen flow rates. The crystallization and oxidation of the coatings is assessed along with corrosion resistance. As thermal energy in the plasma jet increases, the melting fraction and oxidation of particles in the coating increases as does porosity. All of these factors have an effect on the corrosion resistance of Cu-based bulk metallic glass coatings and their relative impact is discussed.

In this investigation, carbon nanotube (CNT) aluminum composite coatings are produced by kinetic spraying. Electrical and mechanical properties are evaluated and compared with those of cold-sprayed pure aluminum coatings. The CNT aluminum composite coatings exhibited higher conductivity and hardness than the pure aluminum, which is attributed to the high electrical conductivity and dispersion hardening effects of embedded CNTs in the aluminum matrix.

Manufacturing of diamond abrasive wheel has been achieved through kinetic spraying in order to simplify the manufacturing process and improve the mechanical properties. However, size of the initial feedstock diamond particles is reduced by fracturing during the process. Uniform distribution of diamond particles in the coating layer is significantly important for obtaining grinding properties of diamond abrasive wheel. In this study, optimized nickel thin film which is coated around the surface of diamond particle was used to prevent the fracture of diamond particles during spraying and improve the properties. Thickness of the nickel thin film was optimized by ABAQUS 6.7-2 finite element analysis software as 3 µm for 20 µm diamond and bronze particles. Fraction and size distribution of the diamond particles present in the coating were analyzed through Scanning Electron Microscope (SEM) and Image analyzer methods.

In this study, interconnect layer of solid oxide fuel cell (SOFC) was built up from spray-dried La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) and blended LSCF-Ag through atmospheric plasma spraying (APS). Microstructure and phase of each coating was analyzed through scanning electron microscopy (SEM) and X-ray diffraction (XRD) respectively. Furthermore, bond strength, micro-hardness, thermal cycle test and oxidation test were performed and compared. The coatings prepared from spray-dried LSCF have higher porosity and cracks at inter-particle boundaries. However, the coatings with silver addition presented reduced cracks and porosity due to relatively high ductility of silver, resulting in higher mechanical properties.

In this study, Al-Sn binary alloy coatings were prepared with Al-5wt.%Sn (Al-5Sn) and Al-10wt.%Sn (Al-10Sn) gas atomized powders by low pressure and high pressure cold spray process. The microstructure and microhardness of the coatings were characterized. The as-sprayed coating were heat treated at 150, 200, 250 and 300 °C for 1 hour, respectively. The effect of heat treatment on microstructure, microhardness and content of Sn phase of the coatings were investigated. The bonding strength of as-sprayed and heat treated Al-Sn coatings were also studied. The results show that the dense and well-bonded Al-10Sn coating can be deposited by low pressure with helium gas while Al-5Sn coating by high pressure cold spray with nitrogen gas. The content of Sn for both Al-5Sn and Al- 10Sn in as-sprayed coatings are consistent with that in feed stock powders. The coarsening and/or migration of Sn phase in both coatings were observed when the annealing temperature exceeds 200 °C. Furthermore, the microhardness of the coatings decreased significantly under the annealing temperature of 250 °C. EDAX analysis shows that the heat treatment has no significant effect on content of Sn phase in Al-5Sn coatings. Bonding strength of as-sprayed Al-10Sn coating is slightly higher than that of Al-5Sn coating. Annealing under 200 °C can increase the bonding strength of Al-5Sn coatings.