Materials Science Forum Vol. 941

Abstract: Nature-inspired superhydrophobic surfaces have received immense industrial and academic interest due to their non-wettability and self-cleaning properties. To fabricate superhydrophobic silicone rubber surfaces, a simple, environmentally friendly atmospheric-pressure plasma treatment was applied. The effect of diverse plasma processing parameters on the final wettability behavior of the substrates, including plasma power, plasma frequency, number of passes, plasma jet speed, plasma cycle time and distance between the nuzzle outlet and substrate, were analyzed by means of design of experiments (DoE). Surface chemical characterization illustrated the influence of plasma treatment on the chemical composition of the produced silicone rubber. Furthermore, the presence of microstructures as well as the chemical composition of the surface was confirmed using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy analysis.

Abstract: Effects of the surface-treated A5052 aluminum alloy on the adhesiveness of joining dissimilar materials, such as A5052 aluminum alloy sheet and polyamide resin sheet, was examined to manufacture a multi-material. Various surface treatments for the A5052 sheet were performed. The hot melt adhesive sheet comprising polyamide resin was used as the adhesive. The shear strength of adhered specimens was measured via tensile testing, and the shear strength was made to be the joining strength. Using various surface treatment techniques, oxidation films with different hole sizes and surface roughness were formed on the A5052 aluminum sheets. The joining strength of the surface-treated specimens was the lowest, whereas those joined via anode electrolysis exhibited the highest joining strength. These differences in joining strengths were owing to the anchor effect and chemical interfacial bonding force.

Abstract: In this study, the effect of the surface structure and hydrogen on the fatigue strength of electroless Ni-P plated Al-2%Cu alloy was investigated. As the results, the following points were clarified. Large precipitates were recognized near the specimen surface of the furnace-cooled Al-Cu alloy, but these were not recognized in the aged Al-Cu alloy. Fatigue strength of the Al-Cu alloy specimen subjected to Ni-P plating after a furnace cooling treatment was overall reduced rather than one of the non-processed specimens. Fatigue strength of the Al-Cu alloy specimen subjected to Ni-P plating after the aging treatment showed a clear increase in comparison to one of non-processed materials. In the Al-2%Cu alloy specimens subjected to Ni-P plating after the furnace cooling treatment or aging treatment, a clear hydrogen desorption was recognized. On the other hand, there was only hydrogen desorption from a few of the non-processed specimens. It is considered that the poor fatigue strength of the plating materials is mainly due to the interaction between the surface precipitates and hydrogen gas.

Abstract: Low Al single-phase magnesium alloy surfaces with dense magnesium oxide films were uniformly formed. The films were deposited with a radio frequency magnetron sputtering process with a planar magnetron sputtering system. The thickness of deposited magnesium oxide thin films was around 240 nm. According to the XRD results, a magnesium oxide phase film was formed on the substrate. The surface was uniform, and no cracks or exfoliation were observed. The deposited magnesium oxide film did not have any cracks or pores, and the surface of the sample was covered by magnesium oxide. The hardness of the magnesium oxide-coated magnesium alloy reached around Hv200, while that of the uncoated Mg-alloy was around Hv80. Moreover, the Vickers indenter under a 10-mN load indented the magnesium alloy substrate coated with the magnesium oxide film to a depth of around 640 nm, while that for the uncoated magnesium alloy substrate was around 620 nm. Meanwhile, the elasticity value for the magnesium alloy substrate coated with magnesium oxide film was around 5.3×10¹⁰ Pa, while that of the uncoated magnesium alloy substrate was around 4.2×10¹⁰ Pa.

Abstract: Cold spray utilizes supersonic jets of compressed gas to accelerate powder particles at high velocities. A coating is formed on a substrate by the impact and deformation of particles. Laser Shock consists in illuminating a sample with a pulsed laser to generate a high pressure shock. Cold spray and laser shock are extremely dynamic processes (time scales of about 10-100 ns). In this paper, applications of laser shock for the study of cold spray are presented. A powder particle of a given size and morphology can be laser shock accelerated at cold spray velocities, finally hitting a substrate in a controlled experimental simulation of the process. Results allow also the characterization of powder materials, through the comparison of deformed particles with numerical impact simulations and the fitting of a plasticity model. Two main advantages compared to the split-Hopkinson pressure bar emerge: deformation rates are closer to cold spray conditions and powders are directly tested, rather than macroscopic cylinders. Laser shock can also be used to measure adhesion and internal cohesion of cold-sprayed coatings (LAser Shock Adhesion Test, LASAT). Cold LAser Shock Spray (CLASS), consisting in laser shocking a coating to re-spray it, can be used to characterize property gradient within a coating or as a new spraying process. Laser shock techniques can prove beneficial for the knowledge of powder materials, which is key for advances in cold spray and other powder based processes. Moreover, the combination of the two techniques could lead to hybrid processes.

Abstract: This study aims at experimentally revealing the effects of damages/fractures in HAp coating layer of acetabular cups on loosening behavior of the acetabular cups. Aseptic loosening is occurred due to degradation of fixing force of acetabular cups by biological effects or mechanical loading. However, effects of mechanical loading on loosening behaviour have not been observed yet. In order to simulate cyclic loading conditions of gaits, a testing system which can load entire components of joint including acetabular cups and stem parts was designed. Moreover, by applying two positions of AE sensors during fatigue testing, it was possible to observe the damage behavior of HAp coating. AE measurement detected different failure modes of HAp coating, which were locally occurred at an edge part of the acetabular cup due to stress singularity at that region. In the cases of changing fixation angles, even though damages in simulated cancellous bone surrounding acetabular cups were less occurred, extents of rotational displacements were compatible with the one in an original fixation angle.

Abstract: The protection of the titanium based Ti6242S alloy against oxidation at moderate temperature is investigated, through the application on its surface of a 300 nm thick, amorphous alumina film. The latter is processed by metalorganic chemical vapor deposition at 500 °C from dimethyl aluminum isopropoxide. Upon oxidation at 600 °C for 5000 h, an interfacial zone is created between the alloy and the external protective layer, composed of unaffected alumina. In these conditions, the mass gain per unit area is eight times lower than that of the bare alloy, while the hardness of the alloy remains unaffected, revealing negligible oxygen ingress attributed to the efficiency of the protective coating. Finally, alumina coated samples show negligible mass change after 80 one-hour thermal cycles between 50 °C and 600 °C, showing excellent coating adherence on the Ti alloy.

Abstract: This paper deals with some of the latest developments and serial production applications at obz innovation gmbh. With three serial production systems and one for the R&D department, obz innovation gmbh is the leading supplier of cold sprayed coatings. The development of the well known serial production process of the sinusoidal copper coating for hybrid cars is explained. Furthermore our ferritic chromium steel induction coating and our new application paths in this area, an immanent temperature limitation function for safety critical reasons, is shown. An example for a field of research actually examined at obz is power electronics with cold sprayed circuits on an insulating ceramic coating with potential use in fields like automotive and many others.

Abstract: Laser surface hardening, is a process in which a shaped laser beam is scanned across the surface to produce a hard and wear-resistant surface on components. Compared with the conventional surface hardening process, the laser heat treatment offers a number of attractive characteristics such as minimal part distortion, self-quenching and the need for less finishing work. The challenge of laser hardening is the uneven surfaces found in molds such as those with sharp edges or holes. In these cases, due to the differences in the surrounding volume of the material, overheating problems often appear leading to unacceptable treatment results. The purpose of this paper is to present the new technology, “raio” developed by Talens System for laser hardening process. This technology is able to adapt to geometrical singularities of the components to be treated, ensuring the dimensions of the hardened area and hardness values are compliant with the requirements. The main features of the technology for laser hardening are validated on a set of samples of 1.2738 steel with representative discontinuities of molds. Mechanical and microstructural characterizations of the hardened cross sections confirm the advantages of the raio technology in regard to the quality compliance of the laser hardening process. Furthermore, raio offers the same advantages for other laser processes, like softening of critical area or laser cladding for repairing of damaged components.

Abstract: High pressure cold spray has been showing increasing promise and application for structural repairs and coating applications where wrought like strengths are required. For example, numerous applications have been developed for repairing high cost and long lead time parts for the aerospace and defense market, such as aircraft skin panels, titanium hydraulic lines, aluminum valve actuator internal bores, hardened and chromed steel shafts, gas turbine engine parts, magnesium castings, and many more. These processes also have direct application in commercial markets like transportation and heavy industry. In particular, parts with lead times in excess of 12 months have been successfully repaired and re-introduced into service. This saves not only the direct cost of the part, but also returns the system to service much sooner. Additional benefits of field application with a hand-held nozzle assembly are also possible, particularly for power plants, refineries, and other large industrial plant operations. Cold spray consequently has a tremendous opportunity to enhance manufacturing sustainability by repairing parts that previously could only be replaced and recycled. It is environmentally friendly, as there are no toxic fumes or other harmful emissions from cold spray. Furthermore, because parts are being repaired and refurbished rather than replaced, there is tremendous cost, energy, and overall environmental benefit, making cold spray a “green” technology and an excellent technology for enhancing the long-term sustainability of high value assets.