Metallurgical bonding of coated inserts within metal castings

A method for forming a metallurgical bond substantially free of defects between a metal insert and a cast metal material, comprising the steps of:

• a. coating a first thin layer of metallurgical material having a thickness of 0.5 to 8 mils onto the insert wherein the step of coating includes forming the layer from a material selected from the group consisting of Silver, Antimony, Bismuth, Chromium, Gold, Lead, Magnesium, Silicon, Tin, Titanium, and Zinc, and
• b. casting the cast metal material against the coated surface of said insert in an protective gas environment,
• wherein the insert has a first coefficient of thermal expansion and the cast metal material has a second coefficient of thermal expansion above the first coefficient of thermal expansion and wherein the step of coating includes the step of coating with a metallic material having a third coefficient of thermal expansion greater than the first coefficient of thermal expansion but less than the second coefficient of thermal expansion.

A method for forming a tenacious, substantially defect free joint between an insert and a cast metal material having a melting point below the insert material, comprising the steps of:

• a. coating a thin layer of a metallic material onto the insert wherein the step of coating includes forming the layer from a material selected from the group consisting of Silver, Antimony, Bismuth, Chromium, Gold, Lead, Magnesium, Silicon, Tin, Titanium, and Zinc,
• b. casting the cast metal material against the coated surface of said insert under conditions which maximize the metallurgical bonds between the insert and thin layer of metallic material and between said thin layer and the cast metal while reducing hydrogen absorption to create a bond strength above 8000 psi;
• wherein the insert has a first coefficient of thermal expansion, the first metallic material has a second coefficient of thermal expansion, and the cast metal material has a third coefficient of thermal expansion and wherein the second coefficient of thermal expansion is greater than the first and less than the third coefficient of thermal expansion.