Abstract
Additive manufacturing (AM) offers many advantages for the mechanical design of metal components. However, the benefits of AM are offset to a certain extent by the poor surface finish and high residual stresses resulting from the printing process, which consequently compromise the mechanical properties of the parts, particularly their fatigue performance. Ultrasonic impact treatment (UIT) is a surface modification process which is often used to increase the fatigue life of welds in ship hulls and steel bridges. This paper studies the effect of UIT on the fatigue life of Ti-6Al-4V manufactured by Direct Metal Laser Sintering (DMLS). The surface properties before and after the UIT are characterized by surface porosity, roughness, hardness and residual stresses. Results show that UIT enhances the fatigue life of DMLS Ti-6Al-4V parts by suppressing the surface defects originating from the DMLS process and inducing compressive residual stresses at the surface. At the adopted UIT application parameters, the treatment improved the fatigue performance by 200%, significantly decreased surface porosity, reduced the surface roughness by 69%, and imposed a compressive hydrostatic stress of 1644 MPa at the surface.
Highlights
Additive Manufacturing (AM) offers great promise to the medical [1], aerospace [2], automotive and defense fields [3,4,5]
While Ultrasonic impact treatment (UIT) is widely used in fatigue improvement of welded joints, the aim of this paper is to treat the surface of Ti-6Al-4V
The specimens were tested in a servo-hydraulic 810 Material Test system (MTS)
Summary
Additive Manufacturing (AM) offers great promise to the medical [1], aerospace [2], automotive and defense fields [3,4,5]. AM have been developed, including, Electron Beam Melting (EBM) [7], Selective Laser Sintering (SLS) [8], Selective Laser Melting (SLM) [9], and Direct Metal Laser Sintering (DMLS) [10]. Another advantage of AM lies within the wide range of materials that can be manufactured such as plastics [11], metals [3,12,13,14], ceramics [15], concrete [16] and fiber reinforced polymers [17], among others.
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