Surface Hardness Modification of Selective Laser Melted Ti6Al4V Parts by Sliding Friction Diamond Burnishing

Abstract

Selective laser melting (SLM) is a frequently used additive manufacturing technology for creating metallic, especially Ti6Al4V parts. After the production by SLM usually postprocessing is necessary for several reasons. Here the sliding friction diamond burnishing is applied as postprocessing procedure.In this paper an experimental study of surface hardness improvement of selective laser melted Ti6Al4V ELI cylindrical parts is demonstrated. The surface is modified by sliding friction diamond burnishing as postprocessing machining. The design of experiment method was applied to investigate effect of five factors (two SLM and three machining parameters) on surface hardness modification.It is shown that both SLM and postprocessing factors makes significant effect to the surface hardness improvement, most important ones are laser power, laser scan speed during manufacturing, and the burnishing force as factor of postprocessing. Empirical formulas are fit to measurement data, and visualized by surface plots. Relationship between factors and the surface hardness improvement is strongly nonlinear. In the investigated parameter window burnishing force has always positive effect to surface hardness improvement.Electron microscopic investigations show that change in surface hardness can be related to four main morphological changes: compression of the surface by plastic deformation of protrusions, attenuation of valleys, formation of inner cavities and creation of small protrusions by diamond tool. This paper is an extended paper of a conference paper published in the proceedings book of the XXXI. International Welding Conference (Kecskemét, Hungary).

Study of the Influence of Coating Roughness on the Properties and Wear Resistance of Electrospark Deposited Ti6Al4V Titanium Alloy

“…Various surface modification methods such as ion plasma nitriding [1,2], chemical and physical vapor deposition CVD and PVD [3,4], gas flame spraying [5,6], etc., are currently used to improve the low hardness, relatively high coefficient of friction, tendency to adhesive bonding and intense wear and failure of the titanium and its alloys [1][2][3][4][5][6][7][8]. Complex, energyintensive, expensive installations and complicated technologies, high process time, annealing, recrystallization and thermal deformation of the substrate caused by high temperatures, inability to deposit more thickness coatings and insufficient adhesion, RESEARCH high costs and environmental pollution are some of the main difficulties limiting the use of these methods.…”

Improving the Surface Quality and Tribological Characteristics of 3D-Printed Titanium Parts through Reactive Electro-Spark Deposition

“…For example, laser beam re-passing [15] and laser texturing [16] can solve these problems, but both methods almost double the time and cost of SLM fabrication. The impossibility of good cleaning and a satisfactory reduction in surface roughness is a serious obstacle to the application of this technology for the production of titanium products [17]. Currently, issues of surface quality control of SLM and DMLS products, as well as improving the surface characteristics of titanium and its alloys, are becoming increasingly relevant.…”