Bonding method
A method of bonding a first article to a second article, each article having a respective bond surface. The method comprises interposing a porous interlayer region between the bond surfaces of the first and second articles and subsequently using electrical resistance heating to locally heat the interlayer region under contact pressure to a bonding temperature below the melting temperature of the interlayer and the first and second articles to thereby bond the interlayer to the first and second articles to form a bonded article. The interlayer has a porosity of between approximately 10% and 30%.
1. A method of forming a bonded article, the method comprising:
providing first and second articles, the first and second articles each having a respective bond surface;
providing a porous interlayer region interposed between the bond surfaces of the first and second articles, the interlayer region having a porosity of between approximately 10% and 30%; and
subsequently locally heating the interlayer region under contact pressure to a bonding temperature below the melting temperature of the interlayer region and the first and second articles to thereby bond the interlayer region to the first and second articles to form the bonded article, wherein the step of locally heating the interlayer comprises electrical resistance heating of the interlayer by passing an electrical current through the interlayer region.
2. A method according to claim 1 , in which the porous interlayer region comprises cells having an aspect ratio of less than 3:1.
3. A method according to claim 1 , wherein the porous interlayer region comprises cells having an average diameter of between 0.3 mm and 1 mm.
4. A method according to claim 1 , wherein the cells have an average length of 0.64 mm.
5. A method according to claim 1 , wherein the interlayer has a thickness of between 0.05 mm and 1 mm.
6. A method according to claim 1 , wherein the porous interlayer region has a surface roughness parameter of greater than 25 Ra.
7. A method according to claim 1 , wherein the porous interlayer region comprises
one or more sub-regions higher having a first porosity, and
one or more sub-regions having a second, higher porosity.
8. A method according to claim 1 , wherein the step of providing a porous interlayer region interposed between the bonding surfaces of the first and second articles comprises providing an additive coating on the respective bonding surface of one or both of the first and second articles.
9. A method according to claim 8 , wherein the step of providing an additive coating comprises an additive manufacturing method of at least one or more of cold spraying, laser assisted cold spraying, blown powder laser deposition and vacuum plasma spraying.
10. A method according to claim 1 , wherein the step of providing a porous interlayer region interposed between the bonding surfaces of the first and second articles comprises providing a power beam of a laser or an electron beam, and moving the focus of the beam on a surface of one of the first and second articles to move material of the respective article.
11. A method according to claim 1 , wherein the step of providing a porous interlayer region between the bonding surfaces of the first and second articles comprises forming a porous preform article, and interposing the porous preform article between the bonding surfaces of the first and second articles.
12. A method according to claim 11 , wherein the step of forming the porous preform article comprises an additive manufacturing process.
13. A method according to claim 1 , wherein the porous interlayer region comprises the same material as the bonding surfaces of the first and second articles.
14. A method according to claim 1 , wherein one or more of the first article, second article and porous interlayer region comprises titanium alloy.
15. A method according to claim 1 , wherein the cells have an average width of 0.35 mm.