Iridium Crucible Welding

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An iridium crucible is a key component in the Czochralski method of growing single crystals, such as Lutetium Oxyorthosilicate (LSO) scintillation crystals and YAG laser crystals. This highly-precious material is used in a variety of other high-tech applications including x-ray tubes and thermocouples that measure extremely high temperatures. Furuya Metal Americas Inc, the company that manufactures the iridium crucible, has recently developed an iridium alloy with 40% rhodium that can be melted and used in these devices because it withstands much higher temperature ranges than conventional iridium.

A problem with this iridium crucible is that repeated use causes grain boundaries to expand, which leads to leakage and cracking. This can cause serious problems with the crucible and the crystals produced in it. The iridium crucibles that are used for this purpose are expensive and the cost of repairing them and replacing them is high.

In the present invention a surface conditioning of the bottom wall 40 and the sidewalls 30 of the iridium crucible is performed by way of weld melting, or weld puddling, using a pulsating welder such as a GTAW welder, TIG welder or laser welder. Other patterns of weld puddling may be utilized so long as a substantial portion of the bottom wall and/or the sidewalls are conditioned in this manner.

The conditioned iridium crucibles are then coated with an external coating consisting of zirconium or zirconium oxide. The resulting iridium crucibles have a useful lifetime significantly extended.