Abrasive blast modification of surfaces

Abstract

A metal surface treatment method wherein the surface (10) is simultaneously bombarded with a mixture of abrasive particles (4) and dopant particles (6) which are delivered at a velocity in the range of 50-250 m / sec, and thereby depositing the dopant material on the surface. Also provided is an article (8) having a surface treated by such a method.

Description

FIELD OF THE INVENTION[0001]The present invention relates to surface treatment techniques in the field of materials science.BACKGROUND TO THE INVENTION[0002]Metal surface finish is often provided using particle bombardment. This can vary from material removal using abrasive blasting through to material deposition using cold spraying. The difference in these approaches rests in the energy of the processes. Despite its name, the cold spray process actually uses elevated temperatures. The gas used to carry the particles is heated to a temperature of several hundred degrees, typically between 200° C. and 1000° C., before it is mixed with the bombardment particles. This increases the gas velocity without increasing the line pressure feeding the gas. Typically cold spray processes operate at elevated temperatures but below the melting point of the metallic bombardment particles that are employed. In addition to the thermal energy provided by the heated gas, the kinetic energy of the bomba...

AI Technical Summary

Problems solved by technology

Due to the requirement for the bombarding particle to deform upon impact, there has been limited applicability of this technology to the deposition of non-metallic materials.

Metal surfaces (especially those of titanium and titanium derived alloy) are naturally contaminated in air by a variety of contaminants.

This results in titanium, and most other metals, always being covered in an oxide layer.

As the metal oxide is typically much harder and less reactive than the metal, the ability of the bombarding particles to bond to the substrate is often limited by the properties of the oxide and not by the properties of the underlying metal.

This is also true of cold spray technologies, which are also limited by the properties of the surface that can be treated.

This results in abrasion of the surface, and abrasive blasting is widely used to clean and roughen metal surfaces.

For many applications, this is considered a detrimental effect and further etching or cleaning steps are required to remove the contamination.

However these techniques all require the use of complex coated media which is expensive to produce, and this was deemed necessary as simply blasting with a simple mix of abrasive particles and coating material was not considered due to the expected removal of the coating by the abrasive action.

These laminate layers were prone to poor adhesion and could delaminate.

In particular, the critical particle delivery velocity required to impregnate the surface with a dopant was not well established, and sub-optimal coatings could therefore result.

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