Effect of HIP Defects on the Mechanical Properties of Additive Manufactured Ti6Al4V Alloy

The expanding use of Additive Manufacturing (AM) technology enables engineers and designers to plan and manufacture highly complex geometries that are impossible to manufacture with any other conventional technology. When comparing this with building parts using powder bed technology, the main differences found in the quality of the products concern fracture toughness, fatigue, and inferiority in tensile tests. To overcome these issues, the Hot Isostatic Press (HIP) procedure may be used to improve the material quality by reducing product porosity. Regarding fatigue, the standard procedure consists of HIP and the machining of specimens to their final geometry. However, in many AM parts, geometrical complexity does not enable complementary machining. Recently, some AM vendors integrated in-process milling capabilities into their machines, in an attempt to address this challenge. In this study, the authors examine the effect of the HIP procedure on representative samples in order to demonstrate its effect on the final products of TI-6Al-4V parts. The results indicate that the fatigue limit of HIPed parts can increase by 12%; however, a dramatic decrease in the fatigue limit was observed if any failure in the HIP process occurred. The authors suggest an optional procedure to improve performance in such cases.