Abstract
Ti-6Al-4V is widely used in various fields of modern industry, but it is difficult to obtain an ultra-smooth surface of Ti-6Al-4V due to its poor machinability. In this article, ultraviolet-induced (UV-induced) nanoparticle colloid jet machining was utilized to carry out ultra-precision polishing of Ti-6Al-4V to improve the surface quality. The results of infrared differential spectroscopy before and after polishing show that new chemical bonds such as Ti-O-Ti (Al-O-Ti and V-O-Ti) appear on the Ti-6Al-4V workpiece surface, which indicates that the material of Ti-6Al-4V workpiece is removed through the chemical interaction between TiO2 nanoparticles and workpiece surface in the process of UV-induced nanoparticle colloid jet machining. The comparison of metallographic structure of Ti-6Al-4V before and after polishing shows that the chemical activity and material removal rate of the primary α phase in Ti-6Al-4V is higher than that of the remnant β phase in UV-induced nanoparticle colloid jet machining, which lead to the well-distributed nano-scale surface peaks and valleys at regular intervals on the polished Ti-6Al-4V workpiece surface. After polishing, the longitudinal residual stress on the surface of Ti-6Al-4V workpiece decreases from 75 MPa to 67 MPa and the transverse stress decreases from 13 MPa to 3 MPa. The surface roughness of Ti-6Al-4V workpiece is reduced from Sa 76.7 nm to Sa 2.87 nm by UV-induced nanoparticle colloid jet machining.
Highlights
Titanium alloys have been widely used in aerospace, petrochemical, medical equipment field and other fields in recent years [1,2] due to their strong corrosion resistance, non-toxicity, good biocompatibility and high strength [3]
According to the material removal mechanism of UV-induced nanoparticle colloid jet machining, a large number of hydroxyl (OH) groups produced in the TiO2 colloid under the action of photocatalysis of ultraviolet light [21] can interact with the atoms on the surface of the TiO2 nanoparticles and Ti-6Al-4V workpiece to generate surface hydroxyl groups
UV-induced nanoparticle colloid jet machining, when the TiO2 nanoparticles impact on the Ti-6Al-4V workpiece, an interfacial chemical reaction may take place between the TiO2 nanoparticles and the Ti-6Al-4V surface, in which new chemical bonds and products are generated
Summary
Titanium alloys (most commonly Ti-6Al-4V) have been widely used in aerospace, petrochemical, medical equipment field and other fields in recent years [1,2] due to their strong corrosion resistance, non-toxicity, good biocompatibility and high strength [3]. Current research shows that the surface processing quality of titanium alloys devices has a great influence on their performance [4,5], and the surface roughness of titanium alloys devices will affect the bacterial adhesion on its surface. Too much surface roughness makes the surface wear resistance of titanium alloys implants worse [6,7], which may have a certain impact on human health [8,9]. Reducing the surface roughness is very important for improving the performance of titanium alloys devices. Experts and scholars have done lots of research on the surface polishing process of titanium alloys to improve the surface quality. The effectiveness of various polishing processes based on chemical, mechanical and electrochemical were investigated to establish the effective methods for smooth Ti surface preparation before anodization
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