Deposition of Ti/TiC Composite Coatings on Implant Structures Using Laser Engineered Net Shaping

A new method of depositing hard and wear resistant composite coatings on metal-onmetal bearing surfaces of titanium implant structures is proposed and demonstrated. The method consists of depositing a Ti/TiC composite coating (~ 2.5 mm thick) on titanium implant bearing surfaces using Laser Engineered Net Shaping (LENS®). Defect-free composite coatings were successfully produced at various amounts of the reinforcing TiC phase with excellent interfacial characteristics using a mixture of commercially pure Ti and TiC powders. The coatings consisted of a mixture of coarser unmelted/partially melted (UMC) TiC particles and finer, discreet resolidified (RSC) TiC particles uniformly distributed in the titanium matrix. The amounts of UMC and RSC were found to increase with increasing TiC content of the original powder mixture. The coatings exhibited a high level of hardness, which increased with increasing TiC content of the original powder mixture. Fractographic studies indicated that the coatings, even at 60 vol.% TiC, do not fail in a brittle manner. Various aspects of LENS® deposition of Ti/TiC composite coatings are addressed and a preliminary understanding of structure-property-fracture correlations is presented. The current work shows that the proposed approach to deposit composite coatings using laser-based metal deposition processes is highly-effective, which can be readily utilized on a commercial basis for manufacture of high-performance implants.Mechanical Engineerin

An Experimental Determination of Optimum Foil Joint Conditions for Structural Parts Fabricated by Ultrasonic Consolidation

This paper describes an investigation of the optimum conditions necessary to eliminate defects at foil joints in parts fabricated by ultrasonic consolidation. Tensile test specimens were fabricated with different foil joint conditions of varying degrees of overlap in the deposition layers. They were subjected to tensile tests to determine their mechanical properties. Microstructures of samples were also studied. Experimental results show correlations between foil joint condition and mechanical strength. Sample microstructures also show correlations between the bonding qualities of the foil joints and the strengths obtained. The study highlights an important process parameter to control for fabrication of defect free structural members by ultrasonic consolidation.Mechanical Engineerin

Formation of Al–Al2O3 core–shell nanosphere chains during electron beam melting of γ-TiAl

Several core–shell nanosphere chains were observed in the electron beam melted Ti–48Al–2Cr–2Nb samples. The formation mechanism of such core–shell nanospheres, induced by Al vaporization, during the electron beam melting of γ-TiAl was investigated using the HRTEM, FESEM, STEM, and XRD analyses. The solidification of TiAl/Ti3Al lamellae, in the vicinity of the Al-diminished zones, was disclosed by microstructural studies. The core and shell of the nanospheres were characterized as porous Al and α-Al2O3, respectively. Finally, the formation of core–shell nanosphere chains in the additive manufactured γ-TiAl was schematically illustrated. © 2021 Elsevier Lt

Processing of in-situ aluminium foam-filled stainless steel tube with foam-tube bonding for enhanced crashworthiness

This work aims to achieve superior mechanical properties in in-situ aluminium foam-filled stainless steel 316L tubes by promoting good bonding between the foam and the tube. Towards this end, the stainless steel tubes (inner surface) were electroplated with copper before in-situ foam-filling. Detailed microstructural studies were conducted at the foam/tube interface. In-situ foam-filled tube specimens were subjected to uniaxial compression and three-point bend testing. The axial compression and bending performance of the in-situ foam-filled tubes were compared with ex-situ foam-filled tubes and in-situ foam-filled tubes produced without copper coating. The deformed samples were sectioned and analysed to understand the deformation modes. The results show that copper coating is very effective in promoting good bonding between the foam and the tube during in-situ foaming, leading to considerable improvement in the mechanical performance of the foam-filled tubes. Ex-situ-heat processed (ex-situ-HP) foam-filled tubes (FFTs) and in-situ-uncoated (in-situ-UC) FFTs were found to display approximately 34 % and 46 % increase in specific energy absorption (SEA) as compared to empty-HP tubes. Electroplating of the inner surface of the steel tube with copper before in-situ foam-filling was found to promote good metallurgical bonding between the foam and the steel tube. Because of the enhanced foam-tube bonding, the in-situ-copper coated (in-situ-CC) FFTs were found to display ~61 % and 10 % higher SEA as compared to the empty-HP and in-situ-UC FFTs, respectively. The deformation mechanisms in foam-filled tubes are discussed in detail

Optimized process parameters for fabricating metal particles reinforced 5083 Al composite by friction stir processing

Metal matrix composites (MMCs) exhibit improved strength but suffer from low ductility. Metal particles reinforcement can be an alternative to retain the ductility in MMCs (Bauri and Yadav, 2010; Thakur and Gupta, 2007) [1,2]. However, processing such composites by conventional routes is difficult. The data presented here relates to friction stir processing (FSP) that was used to process metal particles reinforced aluminum matrix composites. The data is the processing parameters, rotation and traverse speeds, which were optimized to incorporate Ni particles. A wide range of parameters covering tool rotation speeds from 1000 rpm to 1800 rpm and a range of traverse speeds from 6 mm/min to 24 mm/min were explored in order to get a defect free stir zone and uniform distribution of particles. The right combination of rotation and traverse speed was found from these experiments. Both as-received coarse particles (70 μm) and ball-milled finer particles (10 μm) were incorporated in the Al matrix using the optimized parameters

Laser powder bed fused Inconel 718 in stress-relieved and solution heat-treated conditions

Inconel 718 superalloy cylindrical rods were fabricated using the laser powder bed fusion (L-PBF) technology in the vertical orientation. The rods were stress-relieved at 980 °C for 15 min before cutting them from the build plate. The microstructure in this condition exhibited a significant amount of undesirable needle-like δ-phase precipitates and a small amount of interdendritic Laves phase that is finer in size. Differential Scanning Calorimetry (DSC) was used to determine the temperatures for solid-state phase transformations and appropriate temperature for solution-treatment. Solution-treatment was performed at 1065 °C for 1 h, followed by air cooling. The microstructures were characterized with specific reference to δ-phase and Nb segregation. Solution-treatment at 1065 °C was found to result in a significant elimination of micro-segregation (mainly Nb), complete dissolution of δ phase, considerable Laves dissolution, and partly undissolved carbide particles (few nm in size). Solution-treatment did not produce a significant change in the grain morphology (columnar dendritic) on a plane parallel to the build direction but more recrystallized and equiaxed grains were formed on a plane perpendicular to the build direction. The hardness of the solution-treated sample is comparable with wrought 718 alloys but lesser (115 HV) than in the stress-relieved condition attributing to the annihilation of dislocation tangles. © 202