Scale adhesion

Large-scale adhesive bonding of steel is of great interest to the automotive and appliance industries because of the opportunities it provides for design flexibility, weight savings, and manufacturing economy. Because of its economic importance. 

In practice, thermal cycling rather than isothermal conditions more frequently occurs, leading to a deviation from steady state thermodynamic conditions and introducing kinetic modifications. Lattice expansion and contraction, the development of stresses and the production of voids at the alloy-oxide interface, as well as temperature-induced compositional changes, can all give rise to further complications. The resulting loss of scale adhesion and spalling may lead to breakaway oxidation " in which linear oxidation replaces parabolic oxidation (see Section 1.10). 

The presence of small quantities of S in steels has little effect on the initial scaling rates in air, but may be detrimental to long-term scale adhesion. Sulphur has, however, been shown to be detrimental to breakaway oxidation in CO/CO2 environments. However, sulphur has been shown to reduce the total uptake of carbon in the steel under CO/C02 and reduce the scale thickening rate. In this context, free-cutting steels were found to oxidise at a significantly lower rate, as did steels subjected to pretreatment in H2S. 

There are a number of industrial and technological areas in which nanoscale adhesion is important. One of the earliest fields concerned with adhesion on this scale was colloid science. Colloid particles lie in the intermediate region between macro and nano, with dimensions typically of the order of hundreds of nanometers up to a few microns. This means that their true contact areas he well within the nano-domain and are influenced by interactions on this length scale. Adhesion between such particles is important, due to its influence on mineral separation processes and on the aggregation of powders, for example, on the walls of machinery or in the forming of medical tablets. In an extraterrestrial context, such... 

Abrasive wear is caused by sharp asperities cutting the plastic fatigue wear is caused by particles of plastic being detached as a result of dynamic stressing on a localised scale adhesive wear is the transfer of plastic to another surface as a result of adhesive forces between the two surfaces. There can also be corrosive wear due to the direct chemical attack on the surface and the term erosive wear is sometimes used for the action of particles in a liquid stream. 

Shimizu, K., Suzuki, E. et al. 2000. Prevention of scale adhesion using surface treatment of coating with organic compound at geothermal power station. In Proceedings World Geothermal Congress 2000, Kyushu-Tohoku, Japan, 28 May-10 June 2000, 3299-3301. 

Protective scale formers Solid solution strengtheners Age hardening strengtheners Carbide strengtheners Improved scale adhesion (spallation resistance)... 

S van der GroenRosmeulen M, Jansen P, Baert K, Deferm L. CMOS compatible wafer scale adhesive bonding for circuit transfer. Proceedings of The International Conference on Solid-State Sensors and Actuators 1997. p 629-632. 

Davey, R. J., Williams-Seton, L., Lieberman, H. F., Blagden, N., Stabilizing a solid-solid interface with a molecular-scale adhesive . Nature 1999, 402, 797-799. 

The Zr addition is not nearly as effective in improving scale adhesion in Fe3Al. 

Fig. 8. Toial weight change (sample + spalled oxide) during lOOh cycles at 1200°C for Kanthal APM and undoped Fe3Al with various O contents. In long-term testing, Zr02-dispersed FeCrA1 showed excellent scale adhesion but A1203 dispersions did not improve scale adhesion and instead shortened the time to breakaway compared to a cast alloy.The extruded FAS appeared to slump and rapidly oxidize.

Tire higher spallation rate of ODS FAS means an increased A1 consumption rate. This reduces the potential lifetime benefits of the high A1 content of Fe3Al [6,11]. Thus, attempts to improve scale adhesion are a critical step in the development of these materials. 

At 1200 °C and 1300 °C, incorporation of a reactive element in Fe3Al as an oxide dispersion is more effective in improving scale adhesion than a comparable elemental addition. It is proposed that this is due to strengthening of the substrate. 

B. K. Tubbs and J. L., Smialek, Effect of sulphur removal on scale adhesion to PWA 1480. In Corrosion and Particle Erosion at High Temperatures, eds. 

J. A. Haynes, Y. Zhang, W. Y. Lee, B. A. Pint, I. G. Wright, and K. M., Cooley, Effects of platinum additions and sulfur impurities on the microstructure and scale adhesion behavior of single-phase CVD aluminide bond coatings. In Elevated Temperature Coatings, eds. J. M. Hampikian and N. B. Dahotre, Warrendale, PA, TMS, 1999, p. 51. 

During injection moulding, i.e., on a very short time scale, adhesion is quite weak. Once the part is carefully extracted from the mould and stored for a certain period of time (weeks or months) the adhesive force increases significantly - sometimes to an extent where silicone and substrate cannot be separated and the silicone rubber will break before the hard and soft components can separate. This quite long storage time leading to the desired adhesion can be shortened substantially by using a heat treatment. 

Understanding molecular-scale adhesion, friction, lubrication, and wear is crucial to modern technologies, such as microelectromechanical systems (MEMS) and hard disk drives.With atomic force/friction force microscopy (AFM/FFM),several studies have shown the correlation of frictional properties of self-assembled monolayers (SAMs) of alkanethiols with their chain lengths and terminal groups. The long chain monolayers (more than 12 carbon units) have lower friction coefficients compared with their short chain counterparts. Recently, Kim et al investigated the effect of the size of chain termination on frictional properties and found that the difference in friction arises predominantly from the difference in the size of the terminal groups. The AFM/FFM has also been applied to study frictional... 

---