Microstructure and wear resistance of Ti6Al4V surfaces processed by pulsed laser

Abstract

When pulsed laser beams deposit spatially and temporally localized power on the metallic surfaces, microstructure and mechanical properties could change significantly. During and after each pulse, the exposed surface experiences a cycle of thermal processes involving extremely high heating and cooling rates, which consequently cause significant microstructure evolution. Changes in mechanical strength follow such microstructural changes. In this work, the influence of pulsed laser processing (PLP) on microstructural evolution, resulting hardness and wear resistance of Ti6Al4V surfaces is investigated. Average pulse power is varied from surface heating to melting regimes in processing. A 2D axisymmetric finite element model of a single pulse is utilized to obtain the heating and cooling histories, and a phase transformation mapping procedure is used to obtain the microstructural evolution. Melting (MZ) and heat affected zones (HAZ) observed at the cross sections of the processed surfaces are found to correlate with the predicted temperature field. The resulting phases in those zones are predominantly martensitic α' and α phase; higher laser power produces thicker martensitic α' surface layers several microns into the processed surface. Nanoindentation, nano/microscale and mesoscale wear tests are then applied to the processed surfaces to identify the effects of microstructure on hardness and wear resistance. The surface processed by higher laser power shows higher hardness and wear resistance compared to the surface processed by low power laser. The hardness and wear resistance of the surface processed by low power laser shows no obvious change from substrate material. Mixture of hard martensitic surface layer and underlying ductile substrate resulting from PLP facilitate superior resistance to abrasive and partly low cycle fatigue wear.

Pulsed-PTA Preparation of B4C-Based Titanium Matrix Cermet

“…A wide range of techniques of TMC fabrication is used nowadays, they can be classified into five categories liquid-phase processes, (2) solid-liquid processes, (3) two-phase (solid-liquid) processes, (4) deposition techniques and (5) in situ processes [29]. Although it is possible to find mentions of TMC deposition by laser-assisted direct deposition [36], [37], [38], [39], [40], it is almost impossible to find a mention in the literature of the possibility of producing TMC by PTA hardfacing method, only Ti Gr. 1 was tested [41].…”

Laser surface modification of metallic implant materials

“…Laser surface modifications can enhance wear resistance and friction properties of the implant [17]. Chen et al [17] demonstrated that surfaces treated with high laser power showed higher hardness and wear resistance than the untreated and surfaces treated by low laser power.…”

“…Low hardness values and poor tribological characteristics of metallic implant materials can be improved by laser powder deposition [18]. Comparing the Ti-6Al-4V substrate characteristics with the characteristics of the Ti-Al intermetallic coating formed on the Ti-6Al-4V alloy surface ( Figure 6), Liu et al [20] noticed that intermetallic coating displays lower friction coefficients due to the higher hardness values since the biometallics hardness and wear resistance are greatly influenced by each other [17][18][19][20].…”

Fretting friction properties of laser surface texture microfilaments

“…In the process of friction and wear, textured surface can effectively reduce the wear and tear, and improve the service life (Rosenkranz et al, 2019). At present, the methods of surface texture processing mainly include laser processing, mechanical processing, chemical etching and so on, among these methods, laser processing is widely used because of its high efficiency, strong penetrating power, small impact on the environment, and can improve the hardness of metal surface (Gualtieri et al, 2009;Chen et al, 2017). Etsion and Burstein (1996) and Etsion (2004) have laid a foundation for the pioneering work of improving tribological properties of laser surface texturing (LST).…”