Process for evaluation of delamination-resistance of hard coatings on metal substrates
AssigneeApple Inc.
InventorsEric W. Hamann, William A. Counts, James A. Curran
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Abstract
This disclosure relates to rapid and repeatable tests that can be used to evaluate the interfacial adhesion of coatings to substrates. In particular embodiments, tests are used to assess the resistance of anodic oxides to delamination from aluminum substrates. The tests can be conducted using standard hardness test equipment such as a Vickers indenter, and yield more controlled, repeatable results than a large sample of life-cycle tests such as rock tumble tests. In particular embodiments, the tests involve forming an array of multiple indentations within the substrate such that stressed regions where the coating will likely delaminate are formed and evaluated.
Claims20
A method of determining an adhesion strength between a metal substrate and a coating that overlays the metal substrate, the method comprising:
- forming indentations extending through the coating and into the metal substrate by applying a pre-defined amount of impact force to a region of the coating using an impact agent, wherein at least two of the indentations are capable of generating residual stresses commensurate with a stress induced by the impact force at the region, and the residual stresses combine to form a detachment force that, when greater than the adhesion strength, is capable of causing a separation of the coating and the metal substrate at the region.
A method of determining an adhesion strength between a metal substrate and a coating disposed over the metal substrate, the method comprising:
- forming indentations within the coating and the metal substrate, wherein the indentations include at least a first indentation and a second indentation that are separated by a pre-defined distance that is sufficient to cause a first amount of strain generated by the first indentation to physically communicate with a second amount of strain generated by the second indentation to form a delamination force at a region of the coating, and wherein the coating delaminates from the metal substrate at the region when the delamination force is greater than the adhesion strength.
A system for determining an adhesion strength between a substrate and a coating that overlays the substrate, the system comprising:
- an indentation tool arranged to form indentations extending through the coating and the substrate by applying a pre-defined amount of impact force at a region of the coating, wherein at least two of the indentations formed by the indentation tool are capable of physically communicating with each other to form a detachment force that, when greater than the adhesion strength, is capable of causing a portion of the coating to separate from the substrate;
- and
- an image processing component capable of determining the portion of the coating that separates from the substrate.
Dependencies are inferred from the claim text.