Harde deklagen, een zaak van economie

Applied Science

Stress in hard metal films

In the absence of thermal stress, tensile stress in hard metal films is caused by grain boundary shrinkage and compressive stress is caused by ion peening. It is shown that the two contributions are additive. Moreover tensile stress generated at the grain boundaries does not relax by ion bombardment. In polycrystalline hard metal films the grain structure evolves during growth, leading to wider grains higher up in the film. The tensile component of the stress in the film is generated at the grain boundaries and therefore depends on film thickness. The effect of ion bombardment is independent of grain size, therefore compressive stress does not depend on film thickness. As a result in polycrystalline films deposited under a bias voltage a stress gradient exists from tensile at the interface to compressive at the top of the film.Materials Science and EngineeringMechanical, Maritime and Materials Engineerin

Impact wear of structural steel with yield strength of 235 MPa in various liquids

The wear of pipelines, used in slurry transport, results in high costs for maintenance and replacement. The wear mechanism involves abrasion, corrosion, impact, and the interaction among them. In this work, we study the effect of impact on the wear mechanism and wear rate. Results show that when the effect of impact is small, the wear mechanism is dominated by electrochemically induced surface modification, which leads to a lower wear rate in a corrosive environment than in a non-corrosive environment. By contrast, when the effect of impact is large, the wear mechanism is drastically altered. In that regime plastic deformation is important. The influence of corrosion in the high impact regime can be neglected. Our findings show the importance of including impact effect in the distinction of wear of slurry pipesMicro and Nano Engineerin

Graphene Synthesis

Precision and Microsystems EngineeringMechanical, Maritime and Materials Engineerin

Experimental discrimination of plowing friction and shear friction

Mechanical, Maritime and Materials Engineerin

Künstler-Bilder. Zur produktiven Auseinandersetzung mit der schöpferischen Persönlichkeit

Contains fulltext : 98765.pdf (publisher's version ) (Closed access)223 p

Stress in sputter-deposited Cr films: Influence of Ar pressure

We studied the tensile stress and grain-width evolution in sputter-deposited Cr films with thickness from 20?nm to 2.7??m. Films were deposited in an industrial Hauzer 750 physical vapor deposition machine at 50–80?°C. The films exhibited a columnar microstructure. A power law behavior of the tensile stress as well as of the average grain width with thickness was observed. Both power exponents were strongly dependent on the Ar pressure during deposition. The power exponent ? for stress varied from 0.26 to 0.79 for the range of Ar pressures used (5×10?3–2×10?2?mbar). The mechanism of tensile stress generation is the shrinkage of the grain boundaries. Assuming the same shrinkage of the grain boundaries all through the layer, the stress and the grain width would be inversely proportional. Indeed, the grain width followed the same power law as the stress at low Ar pressure [? = 0.3(1)], but not at high Ar pressure [? = 0.58(3)]. Transmission electron microscopy showed the formation of numerous voids. At higher Ar pressure the void fraction is significantly higher than at low pressure, thereby diminishing stress generation.Kavli Institute of NanoscienceApplied Science