Coatings coating-substrate system

Although the initial choice of coating material applied for reasons (b) or (c) may be dictated by the particular properties required, the corrosion behaviour of the composite metal coating/metal substrate system must also be taken into consideration in so far as it may affect the maintenance of the desired properties. Consequently, in all cases where protective metal coatings are used the corrosion performance of both coating and substrate require careful consideration. 

A nano scratch tester (CSEM) was employed to carry out the scratch test. A Rockwell diamond tip with a radius of 2 fim was used to draw at a constant speed 3 mm/min across the coating/substrate system under progressive loading of 130 mN maximum at a fixed rate 130 mN/min. The total length of the scratch scar is 3 mm. The critical load (L ) here is defined as the smallest load at which a recognizable failure occurs. The failure can be observed both by the built-in sensors and by the optical microscope. 

Bao, G., Cai, H., (1997) Delamination cracking in functionally graded coating/metal substrate system , Acta Mater, 45(3) 1055-1066. 

It appears then that the role of an interlayer can be predominant in the mechanical stability of a coating on substrate system. Variable thicknesses may attenuate the difference between the residual stresses in the deposit and in the substrate. This should give the system more satisfactory behavior when subjected to external stresses. 

However, both relations cannot be directly applied to thin films or coatings unless their thicknesses are several times, typically 10 times, greater than the indentation depth so that the subsurface deformation beneath the indenter is not influenced by the proximity of interfaces or free surfaces (Burnett and Rickerby, 1987). Those interfaces can be considered for a stratified coating using Buckle s proposal (Buckle, 1971) that the hardness should be expressed as a weighted sum of the hardness of the different layers. In this spirit, a ceramic coating-metal substrate system could be considered a two-layer material the composite hardness Hc of which is then... 

The electrical resistance of coatings is composed of the active (ohmic) and reactive (polarization) resistances. The latter is a resistance to alternating current through the capacity and inductance of the coating-substrate system. Ohmic resistance makes up an insignificant portion of the total electrical resistance of pol3Tner coatings and characterizes electrolyte diffusion in the... 

The capacity of the coating-substrate system characterizes swelling (change in dielectric permittivity) of the coating in electrolytes and pore volume in the coating. 

Plasma nitriding and/or thermal treatment of the coating-substrate system... 

FIGURE 24.10 Cr and A1 distribution in a coating-substrate system for the ordinary IBAD process (a) and for the duplex process, in particular, Implantation + IBAD (b). (From Guglya, A. et ah, Probl. At. Sci. TechnoL, 3(86), 171, 2005. With permission.)... 

Since atmospheric corrosion is an electrochemical process, attempts have been made to develop electrochemical test methods that can predict the corrosion resistance of the coating-substrate system [9.41], [9.42],... 

The interfacial adhesion of a coating—substrate system is of vital importance to the performance and reliability of medical products. The work of adhesion (IVa) describes the energy required during fracture of a coating—substrate interface and is calculated using the surface energies of the coating (yc) and substrate (yj and at the interface (Ycs) ... 

Undoubtedly, the most popular and widely used technique for assessing the adhesion strength of coating—substrate systems (Benjamin and Weaver, 1960 Tangier, 1981, 1984 Burnett and Rickerby, 1987 Bull and Berasetegui, 2006), scratch testing... 

Vlachos, D.E., Markopoulos, Y.P., Kostopoulos, V., 2001. 3-D modelling of nanoindentation experiment on a coating-substrate system. Comput. Mech. 27, 138—144. 

There are a number of different indentation fracture events which might occur in a coating substrate system (Table 1), the occurrence of which will depend on the relative toughness of coating/substrate and any interfaces present. These failure modes will be altered by plastic deformation in the substrate which can lead to the superposition of bending stresses on to those generated by the indentation. 

In this study thin ceramic coatings have been deposited onto both brittle and ductile substrates to assess the fracture behaviour of the coating/substrate system. Niobium... 

Table 1. Fracture events associated with brittle (ceramic) coating/substrate systems.

Table 2. Coating/substrate systems investigated in this study.

S. R. Kim, J.A. Nairn, Fracture mechanics analysis of coating/substrate systems. Part E Analysis of tensile and bending tests, Eng. Fracture Mechanics, 65 (2000) 573 579... 

---