Owing to better mechanical properties and shape memory effect, the NiTi composites fabricated by powder metallurgy are suitable for biomedical implants. However, the excessive porosity and formation of micro-cracks are the major issues related to the NiTi composite. This work focused on developing crack-free dense NiTi composites by newly developed uni-axial compaction die. The work includes the design and manufacturing of uni-axial compaction die. The die was tested by SOLIDWORKS software in a simulated environment. Further, composite samples were successfully fabricated without circumferential micro-cracks at 1910.82 MPa compaction pressure. The effects of compaction pressure on microstructural, densification, and mechanical behavior of NiTi composites were also analyzed. Microstructural characterization shows that the Ni-rich phase increased and the Ti-rich phase decreased with the increase of compaction pressure. The porosity reduces from 17.04 to 8.75% by increasing the compaction pressure from 1273.88 to 1910.82 MPa, and a maximum density of 5.50 g.cm -3 was obtained. The NiTi 150 composite has similar Young's modulus, and compressive strength (6.93 GPa and 94.36 MPa) compared to cortical and cancellous bone. The high compaction pressure also increases the micro-hardness of NiTi composite up to 453.8 HV 0.5 .
A compaction die has an essential role in the powder metallurgy process due to the controlling and ease of processing. The shape and properties of die can significantly affect the features of the final part as the several steps and assessments are involved before design and fabrication of compaction die. This work is an effort to design and manufacture a compaction die that can successfully use for uni-axial compaction of NiTi powder. The design and development of die includes design consideration, 2D drawing, 3D model and processes involved in the fabrication of die. The die design was analyzed by ANSYS 19.1 software in a simulated environment, and the fabricated die was tested experimentally by preparing the composite sample successfully at 1000MPa compaction pressure using universal testing machine. Further, the compaction behaviour, density, compressive strength and hardness of developed NiTi composite have also evaluated.
Several bioceramics are used to enhance the bioactivity of NiTi, but the porous structure of these bioceramics simultaneously degrades the mechanical characteristics of implants. Therefore, NiTiMD composites were successfully synthesised with 0–10 wt.% reinforcement of waste marble dust (MD). Further, the effects of marble dust reinforcement on the physical, mechanical, and bioactive properties of NiTiMD composites were analysed. Field emission scanning electron microscopy images and X-ray diffraction patterns revealed the development of the primary NiTi and few secondary (e.g., NiTi2, Ni4Ti3, and Ni3Ti) phases. The porosity of NiTiMD composites increased from 8.74 to 20.83 % with the increase of marble dust reinforcement. Mechanical characterisation exhibited a two times increment in micro-hardness and bone-like Young’s modulus (3.10–6.93 GPa) and compressive strength (77.57–94.36 MPa). It was observed that the marble dust reinforcement enhanced the bioactivity of NiTiMD composites, and a uniform calcium phosphate (Ca-P) layer was formed on the NiTiMD6 and NiTiMD10 composites. Hence, the NiTiMD6 composite with balanced mechanical characteristics and enhanced bioactivity can be used as a novel material for orthopaedic implants.
Generally, Nickel-Titanium composites are prepared by powder metallurgy (PM) process in which the design and shape of compaction die considerably influence the characteristics of the final products. The formation of circumferential cracks and higher porosity are the major issues of this process. Therefore, the work comprises the design and fabrication of a modified cold compaction die by incorporate one additional part named as liner that prepared the Nickel-Titanium composite without circumferential cracks. The work includes design calculations, modeling and die fabrication. The die design was evaluated by SOLIDWORKS 2017-18 in a simulated conditions, and further examined experimentally by fabricating the Nickel-Titanium composite at 140 kN compaction load using UTM. The results showed that a crack-free dense Nickel-Titanium composite was successfully fabricated by this modified die. The densification, compressive strength and Rockwell hardness of NiTi composite fabricated using this die were achieved upto 86.7 %, 108.29 MPa and 64.2 HRC.
In this study, different in-situ phase development techniques in the aluminium matrix are analyzed based on results obtained by using these methods. Microstructural and mechanical characteristics of aluminium-matrix composites reinforced by in situ titanium diboride (TiB2) have been analyzed in this paper. During the study, it is found that using in-situ methods for phase development in aluminium-based composites is more appropriate than other ex-situ methods. The interfaces between titanium diboride (TiB2) reinforcement and aluminium (Al)matrix are clean, and enhanced mechanical characteristics can be achieved.
A new and enhanced microfine cement system is presented in this paper which can be used in challenging cement squeeze applications. There are numerous cement squeeze jobs conducted during workover operations every year within the State of Kuwait to prevent water influx. A very common challenge encountered during these applications is either low or no injectivity scenarios. Conventional cement slurries at 15.8-lb/gal density have more often than not resulted in failures while performing post job positive and negative pressure tests, even when the pressure tests are repeated multiple times. These failures can often be attributed to the fact that effective squeezing is not possible due to the larger cement particle size across a limited number of perforations due to early bridging of the cement. Similarly, conventional microfine cement systems which have also been used in these applications have had only limited success. To overcome these challenges, an improved and enhanced microfine cement design has been developed which is able to obtain higher compressive strengths at lower slurry densities (e.g. 12.5 to 13.0 lb/gal) versus the 15.8-lb/gal conventional slurries. This microfine cement design can be further modified to be used in high, low, and zero injectivity scenarios. It possesses several unique features including thixotropic, expansion, anti-gas migration, and strength retrogression properties. Initial field trials of the system have been very successful. The application of conventional microfine slurry systems in low injectivity scenarios is relatively common in the industry; however the enhanced microfine slurry design can be utilized in a variety of injectivity scenarios, or even in loss situations across perforations, casing leaks, or across the casing shoe. The new microfine cement slurry design has the potential of avoiding multiple squeeze jobs by achieving successful positive and negative pressure test results in a minimum number of attempts.
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