Comparing Wettability and Frictional Performance of Laser Micro-machined Discrete and Continuous Textures
01 Jan 2021-pp 185-192
TL;DR: In this paper, Dimple and cross-hatch textures are fabricated using laser surface texturing (LST) technique to compare the wettability and coefficient of friction (CoF) of discrete and continuous texture under bio-lubricated condition.
Abstract: TiAl4V is used widely in aerospace and biomedical application due to its high specific strength and good bio-compatibility. Its poor tribological performance restricts usage for hip implant articulation. Various surface characteristics such as surface roughness and wettability affect the tribological behaviour of Ti6Al4V sliding. Surface texturing is the recent technique to modify the surface features and improve the wettability. This study aims to compare the wettability and coefficient of friction (CoF) of discrete and continuous texture under bio-lubricated condition. Dimple and crosshatch textures are fabricated using laser surface texturing (LST) technique. The geometrical parameters such as depth, pitch and area density have been kept the same. Wettability associated with both the textures are analysed by measuring surface contact angles using goniometer. Further, friction behaviour is evaluated for all the textured and non-textured surfaces under biological environment using reciprocating pin-on-disc tribometer. Results show a significant reduction in contact angle for crosshatch texture compared to dimple and non-textured surface. Also, both the texture reduced the friction by 24% compared to non-textured surface.
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TL;DR: In this paper , oriented crosshatch textures were fabricated over Ti6Al4V surface using Nd:YAG laser and the effect of heat treatment over DLC coating morphology, adhesion strength and surface characteristics was analyzed.
Abstract: Superior surface characteristics, tribological performance and adhesion strength are critical for DLC coated surface in hip implant. Incorporating laser surface texturing and heat treatment before DLC deposition can improve surface properties by inducing oxygen diffusion and phase formation. Therefore, oriented crosshatch textures were fabricated over Ti6Al4V surface using Nd:YAG laser. Textured surface was heat treated followed by DLC coating deposition with Cr interlayer. Effect of heat treatment over DLC coating morphology, adhesion strength and surface characteristics was analyzed. Phase formation and bonding behavior at the coating interlayer were characterized and correlated with adhesion strength. Bio-tribological performance of modified surface was evaluated under elliptical sliding contact to replicate hip implant articulation. Increased surface roughness, better wettability and enhanced graphitic characteristics were associated with DLC coating with prior heat treatment. With heat treatment, Cr2O3 and TiO2 phase formation with superior bonding at interlayer demonstrated improved adhesion strength including deformation resistance. Textured, heat treated and DLC coated surface showed relatively increased compressive residual stress with HF1 quality adhesion. The synergic effect of surface texturing and DLC coating achieved lowest friction. Qualitative wear analysis using Raman spectroscopy reveals beneficial effect of heat treatment before DLC coating for long term hip implant application.
9 citations
TL;DR: In this paper , the authors investigated the role of laser scanning and post heat treatment in improving the oxygen diffusion depth and overall surface characteristics of Ti6Al4V surface and found that the combination of LST and heat treatment improves rutile phase fraction, surface hardness and adhesion.
Abstract: The combination of laser surface texturing and heat treatment process was barely investigated in the past, particularly for improved surface characteristics of Ti6Al4V. Hereby, the important role of laser scanning and post heat treatment in improving the oxygen diffusion depth and overall surface characteristics was analyzed. Polished Ti6Al4V surface was scanned using Nd:YAG nanosecond laser and analyzed for the oxygen pickup, phase change and hardness variation. The laser textured surface was heat treated to grow oxide coating over textured surface. In comparison with heat treated surface, the synergic effect of laser scanning and heat treatment improved the surface hardness by 15% and raised the TiO 2 rutile phase fraction from 0.36 to 0.73. The dual engineered Ti6Al4V surface was found to have superior HF1 quality adhesion strength along with the presence of low magnitude tensile residual stress. The increase in oxygen diffusion depth, diffusion coefficient and TiO 2 rutile phase fraction due to synergic effect of laser scanning and heat treatment were associated to the Ti 2 O 3 and C doping assisted anatase to rutile transformation mechanism. • Laser scanning is responsible for oxygen and carbon pickup and forms Ti2O3 phase at the Ti6Al4V surface. • Combination of LST and heat treatment improves rutile phase fraction, surface hardness and adhesion. • Oxygen diffusion depth and diffusion coefficient increase using laser texturing with heat treatment process. • Anatase to rutile transformation is prominent mechanism in laser textured with heat treated Ti6Al4V surface.
6 citations
2 citations
TL;DR: In this paper , the authors combined the laser surface texturing technology and heat treatment process to fabricate a dual surface engineered Ti6Al4V consisting of micro-groove crosshatch pattern texture covered with hard TiO 2 oxide coating to reduce friction and improve the wear resistance at the bio-lubricated interface.
Abstract: This study combines the laser surface texturing technology and heat treatment process to fabricate a dual surface engineered Ti6Al4V consisting of micro-groove crosshatch pattern texture covered with hard TiO 2 oxide coating to reduced friction and improve the wear resistance at the bio-lubricated interface. Crosshatch texture with 25 μm width, 5 μm depth at 25% area density were fabricated using nanosecond Nd:YAG laser over Ti6Al4V surface and then heat treated at 600 °C for 48 hours. XRD result showed rutile TiO 2 phase formation along with the presence of anatase TiO 2 , Al 2 O 3 and Ti 3 O minor phases whereas, the surface hardness was increased to 1538±41 HV. Bio-tribology experiments were carried out for 45 and 90 o oriented micro-groove crosshatch textures, with and without heat treatment, under partially replicating hip implant articulation. Results demonstrated 60% friction reduction corresponding to the 45 o oriented crosshatch texture with heat treatment. Further, the worn-out surface morphology showed reduced wear damage and good wear debris entrapment inside the micro-grooves.
1 citations
TL;DR: In this article , thermal oxidation was performed on micro-blasted Ti6Al4V surfaces for 24 and 48 hours and the electrochemical performance was evaluated using FESEM, EDS, XRD, AFM, and Goniometer.
Abstract: Ti6Al4V alloy is widely used for orthopaedic applications due to its excellent osteointegration, good biocompatibility, great strength-to-weight ratio, and comparable elasticity with bone. However, when this alloy is exposed for long-term in the body fluid, it releases the corrosion products of metals and metal oxides. The released particles react with the surrounding tissue and cause an adverse local tissue reaction (ALTR) which leads to pseudotumor formation, osteolysis (bone degradation). Thus, corrosion is a critical parameter for bio-implants and in this study to minimize corrosion, thermal oxidation was performed on micro-blasted Ti6Al4V surfaces for 24 and 48 h. Surface morphology, phase analysis, surface roughness, and wettability of all types of samples were evaluated using FESEM, EDS, XRD, AFM, and Goniometer. The electrochemical performance was studied in 0.9 wt% NaCl. The combined mechanical and thermal process increases surface roughness and improves the hydrophilic nature of the Ti6Al4V surface by 67 %. The formation of metastable Ti2O3 during micro-blasting and further transformation of anatase and rutile TiO2 during thermal oxidation increases the intensity of anatase and rutile TiO2 formed on the surface and enhances corrosion resistance. Overall, micro-blasting with 48-h thermal oxidation showed 2 times higher corrosion resistance and reduced corrosion rate by almost 50 % as compared with the untreated Ti6Al4V.
References
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TL;DR: In this article, the effect of low and high contact pressures (200 and 30 MPa) on the thickness of bovine serum films was examined under steady state rolling and sliding.
56 citations
TL;DR: Results indicate, that although wear of the coating is lower than seen in older generations of implants, inconsistent quality of the TiN film among different implants indicates the need for strict monitoring of the manufacturing process.
Abstract: Data regarding in vivo performance of titanium nitride (TiN) coated prosthetic femoral heads is scarce, and available studies of older generations of implants demonstrated coating wear in vivo. That is why we conducted a retrieval analysis of 11 femoral heads (articulating in vivo for 1-56 months) with TiN film formed using physical vapor deposition (PVD), to verify if coating failure is a problem in contemporary implants. Retrieved implants were examined using scanning electron microscope, coating roughness was evaluated with a contact profilometer and adhesion was tested using a Rockwell HRC test according to VDI 3824 guideline. Although no gross failure of the TiN coating was observed in our retrievals, all implants had defects typical for PVD coatings, such as pinholes, small titanium droplets and blisters with delaminated coating. In some heads the coating was contaminated with small niobium (Nb) droplets uniformly scattered on the entire surface of the film. Presence of Nb contamination was associated with an increased number and area of other types of defects and poorer coating adhesion. In one component, subjected to multiple dislocations we found severe delamination and cracking of the coating, increased roughness and the presence of third bodies. Our results indicate, that although wear of the coating is lower than seen in older generations of implants, inconsistent quality of the TiN film among different implants indicates the need for strict monitoring of the manufacturing process.
48 citations
TL;DR: In this article, a vibration-assisted machining method was proposed to generate different micro-structured surfaces on cylindrical surfaces and thus to control surface wettability, including micro-dimple arrays, micro-channels and grid patterns of different densities, depths and feature lengths.
Abstract: A vibration-assisted machining method is proposed in this paper to generate different micro-structured surfaces on cylindrical surfaces and thus to control surface wettability. The proposed machining method, the elliptical vibration texturing process, utilizes vibrations/modulations of the cutting depth at an ultrasonic frequency for fast generation of micro-structured surfaces. The configuration and dimensions of these micro-structures, which play a crucial role in the surface’s wettability, can be controlled by carefully choosing the process parameters. Examples of micro-dimple arrays, micro-channels, and grid patterns of different densities, depths, and feature lengths were demonstrated. The resultant water contact angles from different types of micro-structures were measured and compared to establish a relationship between surface wettability and process parameters.
37 citations
TL;DR: DLC coated microdimple arrays were fabricated on hip prosthesis heads and their mechanical, material and surface properties were characterized, and a significant reduction in friction coefficient was found.
Abstract: Diamond like carbon (DLC) is applied as a thin film onto substrates to obtain desired surface properties such as increased hardness and corrosion resistance, and decreased friction and wear rate. Microdimple is an advanced surface modification technique enhancing the tribological performance. In this study, DLC coated microdimples were fabricated on hip prosthesis heads and their mechanical, material and surface properties were characterized. An Electro discharge machining (EDM) oriented microdrilling was utilized to fabricate a defined microdimple array (diameter of 300 µm, depth of 70 µm, and pitch of 900 µm) on stainless steel (SS) hip prosthesis heads. The dimpled surfaces were then coated by hydrogenated amorphous carbon (a-C:H) and tetrahedral amorphous carbon (Ta-C) layers by using a magnetron sputtering technology. A preliminary tribology test was conducted on these fabricated surfaces against a ceramic ball in simulated hip joint conditions. It was found that the fabricated dimples were perpendicular to the spherical surfaces and no cutting-tools wear debris was detected inside the individual dimples. The a-C:H and Ta-C coatings increased the hardness at both the dimple edges and the nondimpled region. The tribology test showed a significant reduction in friction coefficient for coated surfaces regardless of microdimple arrays: the lowest friction coefficient was found for the a-C:H samples (µ = 0.084), followed by Ta-C (µ = 0.119), as compared to the SS surface (µ = 0.248).
32 citations