Application of mechanical surface finishing processes for roughness reduction and fatigue improvement of additively manufactured Ti-6Al-4V parts. (September 2017)

• Record Type: Journal Article
• Authors: Bagehorn, S.; Wehr, J.; Maier, H.J.
• Is Part Of: International journal of fatigue. Volume 102(2017)
• Page Start: 135
• Page End: 142
• Publication Date: 2017-09
• Subjects: High-cycle fatigue -- Additive manufacturing -- Titanium -- Ti-6Al-4V -- Laser beam -- Surface treatments -- Milling -- Micro machining process -- Vibratory grinding -- Blasting -- Surface roughness; Materials -- Fatigue -- Periodicals; Materials -- Fatigue; Periodicals; 620.1122
• DOI: 10.1016/j.ijfatigue.2017.05.008
• Languages: English
• ISSNs: 0142-1123

Abstract

Highlights: High surface roughness R a > 15 μm of 'as built' AM Ti64 surfaces. Substantially low fatigue performance of AM as built Ti64 (∼300 MPa). Decrease of the initial surface roughness by various mechanical surface treatments. Significant increase of fatigue performance due to roughness decrease (400–775 MPa). Abstract: Currently, additively manufactured (AM) parts have a high initial surface roughness after the manufacturing process, which can be a limitation for application in highly stressed and cyclically loaded areas. In the present study, Ti-6Al-4V samples were manufactured by laser beam melting, annealed and hot isostatically pressed afterwards. They showed an initial surface roughness of R a = 17.9 μm depending on their build direction (45°). Subsequently, four different mechanical surface finishing processes were applied separately on plates and fatigue coupons in order to reduce the surface roughness: Milling, blasting, vibratory grinding and a micro machining process. The effectiveness of each treatment is evaluated with respect to the surface topography, as well as the fatigue properties based on axial fatigue tests performed in accordance to DIN EN 6072. The initial roughness could often be reduced to values R a < 1 μm. The roughness decrease led to a substantial increase in the fatigue performance from initially 300 MPa to a maximum of 775 MPa (after 3 × 10 7 cycles).