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Platinum Metals Rev., 1987, 31, (2), 62

A Study of Platinum Alloy Welds

The Effect of Hydrogen Concentration

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Considerable experience of the use of platinum alloys for glass-melting apparatus has now accumulated, and this shows that a key factor determining service life can be the integrity of the alloy in the proximity of welded joints. Brittle fracture of platinum alloys can result from contaminants entering the weld during fabrication or use, and a recently reported investigation by O. D. Smiyan, B. I. Shnaider, D. M. Pogrebiskii, L. A. Potapenko and E. I. Butkova of the E. O. Paton Welding Institute of the Ukraine SSR Academy of Sciences has considered the effect of welding technique on crack initiation and development (Avt. Svarka, 1986, 395, (2), 10–12, 29).

The alloy used was platinum-20 rhodium-10 palladium-0.1 iridium-0.1 gold, in the form of a disc of 0.5 mm thick sheet which had been annealed for 30 minutes at 1000°C. Concentric welds were made by plasma micro-welding, either under an argon+hydrogen atmosphere or without a protective shielding, while the perimeter of the disc was held rigid. Microstructure, hardness and composition were examined and it was concluded that this alloy is highly resistant to crack formation during welding, that the use of the protective atmosphere does not affect the results, and that there is a relationship between welding sequence and the hydrogen distribution. Under unfavourable conditions the local hydrogen concentration can vary by more than 2:1, and may account for the reduced strength of some welded joints.

It is suggested that the formation of concentric welds, where the stresses are expected to increase as the diameter of the circular weld increases, is a convenient way of evaluating the weldability of a material.

An English language translation of this paper appears in Automatic Welding, 1986, 39, (2), 13–15; this cover-to-cover translation of the Russian journal Avtomaticheskaya Svarka being sponsored by the British Library Lending Division, and published by The Welding Institute, Abington, Cambridge, England.

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