Muhammad Dilawer Hayat

An easy-to-decompose binder for Ti metal injection molding: Preparation and characterization of feedstock

Impurity control is crucial to Ti metal powder injection molding (Ti-MIM) since titanium is a universal solvent to interstitial elements such as oxygen, carbon and nitrogen. In this study, a low decomposition temperature binder system was developed; the rheological and solvent debinding assessments of the feedstock formulated from this binder were performed. Solvent mixing was employed to prepare homogeneous feedstocks. Effects of powder shape and solid loading on rheological properties were evaluated. After injection molding, a debinding profile was constructed. The debound parts were then characterized by microstructural observation.

Physical and Tensile Properties of NiTi Alloy by Selective Electron Beam Melting

NiTi is characterized as a shape memory alloy that has found interesting applications from aerospace to biomedical engineering. The use of NiTi in biomedical applications is due to its excellent biocompatibility, shape memory and pseudoelastic properties. These properties make NiTi an excellent candidate for many functional designs in biomedical fields. However, difficulties in manufacturing and processing of this alloy are significant hindrance to widespread applications. Advances in additive manufacturing (AM) such as selective laser and electron beam techniques have provided opportunities in manufacturing complex shaped NiTi parts. In this research paper, we demonstrate manufacturing of NiTi parts using a selective electron beam melting (SEBM) technique. Complete evaluation of physical, chemical and mechanical properties was carried out to determine the suitability of SEBM process. Differential scanning calorimeter (DSC), X-ray diffraction (XRD), and metallographic analyses were employed for the thermal and structural characterizations. The obtained results suggest that it is imperative to, and challenging to control the additive manufacturing process in order to obtain the desired microstructures and avoid unwanted texture. An exhaustive heat treatment of the samples after SEBM process might also be necessary.

Development of PEG/PMMA based binders for ti-metal injection moulding

As the world is moving towards green manufacturing, there is an increasing demand for the use of clean and environmentally friendly binder systems in metal injection moulding (MIM) industry. One example of these developed binders is polyethylene glycol (PEG) - polymethyl methacrylate (PMMA) based system. We have systematically evaluated and optimized this binder system, and reported some interesting new results. In this article, we reported the effect of PEG molecular weight on rheological properties of the feedstock and its water debinding behaviour. We also investigated the effects of different surfactants on MIM feedstock rheological and mechanical properties, and identified a potential surfactant that enhances compatibility between the binder components and metal powders. Furthermore, we reported an interesting problem – ‘voids formation’, which is associated with PEG crystallization. To minimize this void formation a crystallization inhibitor is incorporated in the PEG/PMMA system, thereby eliminating the void formation while maintaining the clean nature of this system. This paper is concluded with some new thoughts with regard to binder design.

Effects of Open Atmosphere Solutionizing Treatment on the Microstructural and Mechanical Properties of Porous 60NiTi Parts

Titanium alloys have been widely used for medical implants due to their good biocompatibility and excellent corrosion resistance. 60NiTi, an intermetallic nickel-titanium alloy containing approximately 60 wt.% Ni and 40 wt.% Ti, is a promising material for medical components such as implants and prostheses. 60NiTi is hard with good biocompatibility, highly corrosion resistant and has relatively low stiffness. In this study, conventional press-and -sinter method was employed to produce porous 60NiTi parts suitable for general bone replacement applications such as spinal and cranial inserts. The effect of solution treatment in a non-protected furnace and water quenching on the mechanical and microstructural properties of 60NiTi were investigated. It was found that this procedure produces a hard integral ceramic layer, a complex mixture of nickel and titanium oxide compounds, on the surface and around the pores of 60NiTi parts. Results showed that this heat treatment procedure causes the embrittlement of the parts due to an increase in oxide content. However, the produced ceramic surface can also enhance the resistance to corrosion, which is beneficial from a biocompatibility point of view.

Microstructure Characterization of In Situ Ti-TiB Metal Matrix Composites Prepared by Powder Metallurgy Process

Metal matrix composites (MMCs) are the new generation materials that combine both the metallic properties (ductility and toughness) and ceramic characteristics (high strength and modulus), leading to higher strength in shear and compression, at higher service temperatures. Titanium matrix composites possess light weight, high strength and good corrosion resistance and are used as structural materials in automobiles and aerospace industries. In the present study, in situ Ti-TiB composites were fabricated by reinforcing (2, 5, 10 and 20 wt. %) TiB2 powder (mean size <10 microns) into titanium powder (mean particle size ~26.58 μm) and subsequently consolidated by vacuum sintering at 1300 °C for 3 h. X-ray diffraction, scanning electron microscopy (SEM) and density measurements were carried out to characterize the prepared composites. The results showed that all compositions led to high density composites, and the hardness of the composites increased with an increase in the amount of reinforcement. The mechanism of vacuum sintering is yet to be understood in the consolidation of composites and the detailed evolution of microstructure needs to be analysed.

Study of a Binder System for Ti-MIM: A Potential Low Temperature Backbone Polymer

Impurity control remains to be a challenge to titanium metal injection moulding (Ti-MIM). Much attention has been paid to polyethylene glycol (PEG) based binder systems due to the eco-friendly and water-soluble feature of PEG. In this study, a new easy-to-debind PEG/polypropylene carbonate (PPC)-based binder system (76% PEG+17% PPC+3% polymethyl methacrylate (PMMA)+2% stearic acid (SA)+2% polyvinyl acetate (PVAc)) was developed. The rheological properties of the feedstocks prepared with the binder system in different proportions were assessed. Debinding behaviours of the moulded samples and impurity contents of oxygen (O), carbon (C), and nitrogen (N) of the thermal debound specimens were investigated as well.