Process for evaluation of delamination-resistance of hard coatings on metal substrates

Patent metadata

Field	Value
Publication number	US-9869623-B2
Application number	US-201514678881-A
Country	US
Kind code	B2
Filing date	Apr 3, 2015
Priority date	Apr 3, 2015
Publication date	Jan 16, 2018
Grant date	Jan 16, 2018

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.

First claim

What is claimed is:

1. 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.

2. The method of claim 1 , wherein the at least two indentations are separated by a pre-defined distance that is sufficient for physical communication with each other at the region.

3. The method of claim 2 , wherein the pre-defined distance between the at least two indentations is less than three times an average diameter of the at least two indentations.

4. The method of claim 1 , wherein the indentations are arranged according to an array of rows and columns.

5. The method of claim 1 , wherein the pre-defined amount of impact force is constant.

6. The method of claim 1 , wherein the pre-defined amount of impact force is individually adjustable.

7. The method of claim 1 , further comprising:
determining a portion of the coating that is separated from the metal substrate at the region.

8. The method of claim 1 , wherein the region is defined by edges of the indentations.

9. The method of claim 1 , wherein the impact agent includes an indenting tool having a symmetric shape that is capable of forming corresponding symmetrically shaped indentations.

10. The method of claim 1 , wherein the impact agent has a mass that is between 500 grams to 50 kilograms.

11. The method of claim 1 , wherein the metal substrate is at least one of aluminum or aluminum alloy, and the coating is aluminum oxide.

12. 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.

13. The method of claim 12 , wherein the indentations are formed by an impacting agent having a mass that ranges between 500 grams to 50 kilograms.

14. The method of claim 12 , wherein the first and second indentations are adjacent to each other.

15. The method of claim 12 , wherein the indentations are formed by using an indentation tool arranged to deliver a pre-defined amount of impact force on the coating and the substrate.

16. The method of claim 12 , wherein the indentations are formed within the coating and the metal substrate by an indentation tool that delivers a pre-defined amount of impact force in a direction that is generally perpendicular to a surface of the coating.

17. 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.

18. The system of claim 17 , wherein the indentation tool delivers the pre-defined amount of impact force in a direction that is generally perpendicular to a surface of the coating.

19. The system of claim 17 , wherein the indentation tool is capable of adjusting the pre-defined amount of impact force for the indentations.

20. The system of claim 17 , wherein the indentations are arranged according to an array of rows and columns.

Assignees

• Apple Inc

Inventors

• Hamann Eric W
• Counts William A
• Curran James A

Classifications

• G01N19/04 Primary

  Measuring adhesive force between materials, e.g. of sealing tape, of coating · CPC title

• G01N3/42

  by performing impressions under a steady load by indentors, e.g. sphere, pyramid (G01N3/54 takes precedence) · CPC title

• G01N2203/0286

  Miniature specimen; Testing on microregions of a specimen · CPC title

• G01N3/48 Primary

  by performing impressions under impulsive load by indentors, e.g. falling ball (G01N3/54 takes precedence) · CPC title