Damage Tolerance Evaluation of E-PBF-Manufactured Inconel 718 Strut Geometries by Advanced Characterization Techniques

Abstract

By means of electron beam powder bed fusion (E-PBF), highly complex lightweight structures can be manufactured within short process times. Due to the increasing complexity of producible components and the entangled interplay of damage mechanisms, common bulk material properties such as ultimate tensile or fatigue strength are not sufficient to guarantee safe and reliable use in demanding applications. Within this work, the damage tolerance of E-PBF-manufactured Ni-based alloy Inconel 718 (IN 718) strut geometries under uniaxial cyclic loading was investigated supported by several advanced measurement techniques. Based on thermal and electrical measurements, the failure of single struts could reliably be detected, revealing that continuous monitoring is applicable for such complex geometries. Process-induced surface roughness was found to be the main reason for early failure during cyclic loading. Thus, adequate post-processing steps have to be established for complex geometries to significantly improve damage tolerance and, eventually, in-service properties.

Influence of the Miniaturisation Effect on the Effective Stiffness of Lattice Structures in Additive Manufacturing

“…Materials subjected to a phase change upon solidification, such as Ti6Al4V, are less sensitive due to local microstructural changes inhibiting the miniaturisation effect, which enables accurate prediction of the mechanical behaviour using constitutive models for structures with few manufacturing defects. Other common additive manufacturing materials such as 316L, Ni-base alloys [55], and AlSi10Mg [56] are strongly impacted by the miniaturisation effect. This effect, among others, is generally not taken into account in analytical or finite element models, where typically isotropic and size-independent properties are assumed.…”

Heat Input Effect on Microstructure and Mechanical Properties of Electron Beam Additive Manufactured (EBAM) Cu-7.5wt.%Al Bronze

“…Factoring the importance of heat and mass transfer conditions in EBAM layer deposition, the entire near net shape article formation was reported on the AISI 316 [14,15] and Al-6wt.%Mg alloys [16]. Controlling the EBAM deposition parameters ensured forming thin-walled heat resistant nickel alloy articles with the desired shape [17,18] and microstructure [19], as well as complex-shaped sandwich-panels from Ti6Al4V [20].…”

Novel method for in situ damage monitoring during ultrasonic fatigue testing by the advanced acoustic emission technique

“…under cyclic stresses. Whereas the use of the AE technique during conventional low-frequency cyclic loading is a classic topic in the field of the AE research [15][16][17], 2 the AE method has not been applied to USFT so far, to the best of our knowledge. The likely reason for this is the severe noise level of the ultrasonic experimental setup interfering strongly with the AE frequency response.…”