Tailored heat treatments to enhance performance in additive manufactured HAYNES® 282® superalloy

Abstract

While additive manufacturing (AM) has made considerable strides towards industrialization in recent years, its application to superalloys is still limited. This is in part because superalloys manufactured by AM often show anisotropic mechanical properties and creep performance inferior to their cast or wrought counterparts. HAYNES® 282® (282 alloy) is one such alloy which originated in wrought form but has been rapidly adopted in AM. However, AM 282 alloy currently shows deficient high temperature performance relative to wrought 282 alloy, especially when conventional heat treatment is applied to the AM alloy. This study aims to understand how AM and specifically powder bed fusion – laser beam (PBF-LB) processed 282 alloy compares to wrought 282 alloy in terms of microstructure and mechanical properties, and how these can be improved by different heat treatment regimes. 282 alloy manufactured by PBF-LB was subjected to three different solution heat treatments: the conventional solution heat treatment at 1135 °C, a high temperature solution treatment at 1250 °C, and hot isostatic pressing (HIP) at 1250 °C. All materials were double aged at 1010 °C and 788 °C. Mechanical testing showed that solution treatments at 1250 °C reduced anisotropy relative to the typical 1135 °C solution treatment, especially at high temperature. Most significantly, creep rupture life at 927 °C and 89 MPa was doubled (reaching >300 h compared to 115 h for wrought), and minimum creep rate was reduced by an order of magnitude even compared to the wrought counterpart. The improved high temperature mechanical performance was correlated with more equiaxed and coarse grains, tortuous grain boundaries, frequent twins, and specific grain boundary microstructure. The study highlights the critical role of grain structure in high temperature performance, and demonstrates the necessity of tailored heat treatments for enhancing the properties of AM superalloys¹.