Investigation of the High-Cycle Fatigue Life of Selective Laser Melted and Hot Isostatically Pressed Ti-6Al-4v.

摘要

Experimental research was conducted on the effectiveness of Hot Isostatic Pressing (HIP) to improve the high-cycle fatigue life of Selective Laser Melted Ti-6Al-4v (SLM Ti-64). A thorough understanding of the fatigue life performance for additively manufactured parts is necessary before such parts are utilized in an operational capacity in Department of Defense (DoD) systems. Such applications include the rapid, on-demand fabrication of replacement parts during contingency operations or the production of light-weight topology-optimized components. This research assesses the fatigue life of SLM Ti-64 test specimens built directly to net dimensions without any subsequent surface machining. The configuration is designed as representative of end-use parts where further surface machining is unavailable or undesirable. Past research suggests utilization of HIP as a densification process to reduce the negative impact on fatigue life from internal porosity within SLM Ti-64. The impact of HIP on the rough surface of SLM Ti-64 to remove stress concentrations on the surface is not addressed in literature. The experimental data from this research demonstrates HIP improves high-cycle fatigue-life of un-machined test specimens by 61.4% at a maximum stress level of 500 MPa and 102% at a maximum stress level of 300 MPa.