Aluminum-silicon diffusion coated alloy products

A metal alloy product having a diffusion coating on at least one surface, the product comprised of:

• a workpiece formed from an iron, nickel, cobalt or copper base alloy, the workpiece having at least one surface to which a diffusion coating is applied,
• an aluminum silicon diffusion coating diffused into at least one surface of the workpiece, the diffused coating having a thickness greater than 180 microns,
• wherein the diffusion coating is applied by:
• a. preparing a diffusion mixture consisting essentially of by weight 1% to 5% aluminum, 0.5% to 5% silicon, 0.25% to 3% ammonium halide activator and the balance an inert filler;
• b. placing the diffusion mixture in a retort with the alloy product to be coated so that the diffusion mixture covers those surfaces of the product which are to be coated;
• and
• c. heating the retort to a sufficiently high temperature to cause aluminum and silicon in the mixture to diffuse onto at least one surface of the alloy product forming an aluminum silicon coating.

A metal alloy product having an aluminum-silicon diffusion coating on at least one surface, the aluminum and silicon diffusion coating being at least 200 microns thick and formed by the steps of:

• a. preparing a diffusion mixture consisting essentially of by weight 1% to 5% aluminum, 0.5% to 5% silicon, 0.25% to 3% ammonium halide activator and the balance an inert filler;
• b. placing the diffusion mixture in a retort with the alloy product to be coated so that the diffusion mixture covers those surfaces of the product which are to be coated;
• and
• c. heating the retort to a sufficiently high temperature to cause aluminum and silicon in the mixture to diffuse onto at least one surface of the alloy product forming an aluminum-silicon coating having a thickness of at least 200 microns.