The effect of substrate's heat treatment on microstructural and mechanical evolution of transient liquid phase bonded IN-738 LC

• Published in: Materials & design Vol. 89; pp. 611 - 619
• Main Authors: Shakerin, Sajad, Omidvar, Hamid, Mirsalehi, Seyyed Ehsan
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 05.01.2016
• Subjects: Aluminum base alloys; Base metal; Bonding; Enrichment; Hardness; Heat treatment; Inconel-738; Liquid phases; Nickel base alloys; Shear strength; Solid solution; Solidification; Superalloys; TLP bonding; Shear strength; Heat treatment; Solid solution; TLP bonding; Inconel-738
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2015.10.003

Transient liquid phase (TLP) bonding of Inconel-738 LC superalloy was investigated using AMS 4777 filler alloy. The bonding was performed at 40 and 80μm gap sizes at sufficient time in order to achieve complete isothermal solidification. Solution treatment (1120°C/2h) was carried out in two different sequences, one before and the other after TLP bonding of the base metal accompanying subsequent aging treatment (845°C/24h) which are called HT-A and HT-B, respectively. In both cases, no morphological changes in diffusion affected zone (DAZ) precipitates were observed. However, line scan analysis indicates enrichment of base metal alloying elements (Ti, Al) at isothermal solidification zone (ISZ) of heat treated samples, particularly HT-A joints resulted in increased hardness of the centerline. In addition, improved shear strength was seen in heat treated joints conforming to the ductile fracture surfaces. The maximum hardness of 759Hv and the highest shear strength of 565MPa in the joint area, were found in HT-A condition with 40 gap size. Enhanced mechanical properties were mainly controlled by solid solution strengthening mechanism. [Display omitted] •Gamma prime phase in the solution treated sample tended to be spherical than cubic.•The EDS map confirmed inter diffusion between the insert metal and the base metal.•The hardness profiles of ISZ and DAZ were seen to elevate in heat treated conditions.•Finer dimples were found in HT-A sample respect to higher shear strength.