The possibility of forming a TiN dispersed composite layer on steel was studied by preplacement of titanium powder on steel surface and melting under TIG (Tungsten inert gas) torch in a reactive environment. The surface melting of preplaced 1.8 mg/mm2 Ti powder was performed under TIG torch with energy inputs of 324,378 and 432 J/mm in a pure nitrogen environment. With these melting conditions, the powder layer along with a thin layer of the substrate melted and produced a melt pool of around 1mm thickness. The resolidified melt layer consisted of dispersion of TiN dendrites in ferrite matrix and thus a composite of TiN in ferrite is created on the steel surface. The concentration of dendrite population was found to be higher nearer the melt surface compared to the deeper depth. A maximum surface hardness of about 2000 Hv was developed at the surface when glazed with an energy input of 432 J/mm and the hardness decreased gradually away from the surface. The hardness development is directly related to the concentration of TiN dendrites.
In this study an attempt has been made to produce titanium-aluminium dispersed hard nitride layer on mild steel surfaces by preplacement of 50 % Ti and 50 % Al powder mixture and then melting with TIG torch under nitrogen environment. Parameter such as heat input of the torch was varied between 540, 608 and 675 J/mm and its effect on the resolidified melt pool was studied. Glazing under all energy inputs produced more than 1mm thick resolidified clad layer. The microstructural analysis revealed the clad layer with dispersion of dendrites of Ti-Al nitrides and Ti- Al intermetallic in ferrite matrix. The concentration of dendrites were found to be maximum near the surface and decreased at deeper depths.The maximum hardness of the modified surface layer was found to be 900 Hv compared to180 Hv of the mild steel substrate.
The formation of hard surface layer on steel provides a protective coating against wear, thermal loads and corrosion. In the present work a hard composite layer is formed on steel surfaces by preplacement of titanium powder and melted under nitrogen environment. Surface melting was conducted using TIG torch with different energy inputs. The microstructure and the morphology of the melt tracks were investigated using SEM and X-ray diffraction. The in-situ melting of titanium powder in nitrogen atmosphere produced dendritic microstructure of titanium nitride. The melt layer contained dispersed TiN, Ti2N dendrites highly populated at the surface compared to the deeper melt and gave a maximum surface hardness of around 1927 Hv. The wear property of the melt track was investigated using pin-on-disk tribometer at room temperature. The modified surface layer gave a low friction value of 0.12 and wear rate of 0.007895 ×10-4 compared to 1.648 × 10-4 mm3/N/m for the uncoated steel surface.
successful design of folding bicycle should take into account the function, material properties, and fabrication process. There are some other factors that should be considered in anticipating the behavior of materials for folding bicycle. In order to understand the relationship between material properties and design of a folding bicycle and also for the future direction in new materials with new design, a comprehensive study on the design under different conditions are essential. Therefore, a systematic study on the relationship between material properties and design for folding bicycle has been performed. The advantages and disadvantages matrix between conventional bicycle and folding bicycle is presented for better understanding of the materials properties and design. It was found that the materials properties of the folding bicycle frame such as fatigue and tensile strength are the important properties for the better performance of the frame. The relationship between materials properties and design is not straight forward because the behavior of the material in the finished product could be different from that of the raw material. The swing hinge technique could be a better technique in the design for the folding bicycle frame.
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