Archive | 2019
Additive manufacturing: effects of defects
Abstract
Abstract Additive manufacturing (AM) is expected to be a promising new manufacturing process for components having complex geometry. High-strength or hard steels and also light metals such as Ti and Al alloys are expected to be used for the aerospace and automotive industry components having complex shapes which need special costly casting and welding processes if traditional manufacturing methods are applied. The advantages of AM have been emphasised, especially for high-strength or hard steels, which are difficult and costly to manufacture by traditional machining to complex shapes. However, a disadvantage or challenge of AM is the presence of defects which are inevitably produced by the manufacturing process. Until now the papers which focused on the quantitative evaluation of defects are relatively sparse among the flood of publications. Without strict and reliable quality control of components regarding defects, we cannot positively admire the advantages of AM as the new technology. In this chapter, the method of quantitative evaluation of defects for two typical AM materials, Ti–6Al–4V and Nickel-based superalloy 718, will be explained. This chapter focuses on the effects of defects, surface roughness and the Hot Isostatic Pressing (HIP) process on the fatigue strength of Ti–6Al–4V and on the effects of build-up direction and defects of the Nickel-based super alloy 718 manufactured by AM. Practical guides will be presented for the fatigue design and development of high quality and high strength for AM materials, based on the combination of the statistics of extremes on defects, and the area parameter model.