A study of Laser weldability of IN-738 Nickel-based Superalloy in a new pre-weld heat treatment condition

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Aina, Johnson Olubayo
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A new pre-weld heat treatment was developed recently for IN 738 superalloy. Therefore, the research described in this master’s thesis was to study the laser weldability improvement of the alloy which had undergone the new heat treatment, FUMT and the results were compared to an existing pre-weld heat treatment, solution heat treatment (SHT). Also, thermomechanical fatigue (TMF) behavior of the welded alloy was investigated. The results showed that IN-738 welded in FUMT condition had about 70% reduction in weld cracking compared to SHT treated alloy. TMF tests showed that at higher strain ranges, the TMF life of the samples of the alloy welded in FUMT condition is comparable to unwelded samples, while at lower strain ranges, welded samples of the alloy in FUMT condition has a higher TMF life than unwelded samples. This shows that welding IN 738 superalloy in FUMT does not degrade the TMF performance of the alloy.
Laser, Superalloy, Weldability, IN-738