S. Dyuti

Wear Behavior of Modified Surface Layer Produced by TIG Melting of Preplaced Ti Powder in Nitrogen Environment

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.

Formation of TiN dispersed composite layer on steel surfaces by Titanium Powder Preplacement and TIG Surface Melting Processes

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.

Effect of Alkali Treatment on Surface Morphology and Properties of Jute Yarns

Due to the environmental issue, natural fibers are day by day becoming attractive to researchers. Natural fiber contains cellulose, hemicelluloses, lignin etc, which are hygroscopic in nature and biodegradable. The lack of surface feature diminishes its properties. So, the surface properties of the jute yarns need to be modified. In the present study, jute yarns were cleaned using 2% detergent and chemically modified by 5, 15 and 25% NaOH solution both at room temperature and 700C for 2 hours and dried in air. The structural and morphological studies of the treated and untreated yarns were carried out using Fourier transform infrared spectroscopy (FT-IR) and Scanning electron microscopy (SEM). The thermal and mechanical behaviour of the yarns were analyzed using Differential scanning calorimetry (DSC) and Instron Universal testing machine. The results show the improvement in mechanical strength of the yarns due to the change in crystalinity after alkali treatment. Also, the thermal decomposition temperature of raw jute yarns decreased from 357.30C to 349.60 C after alkali treatment.

Effects of Processing Parameters on Microstructures and Properties of TIG Melted Surface Layer of Steel

In order to modify surface structure titanium powder was preplaced on steel surface and melted under TIG (tungsten inert gas) torch in a pure nitrogen environment which formed a resolidified layer of around 1 mm thickness. The preplaced titanium powder content was varied between 1.3 and 1.8 mg/mm2 and melting was conducted with energy inputs of 324 J/mm to 540 J/mm. The modified surface layer was analyzed in terms of microstructure, hardness, surface defects such as cracks and pores. The resolidified layer consisted of dispersion of TiN, Ti2N and TiN.88 dendrites in a ferrite matrix containing titanium. The modified layer showed some defects when melting were performed with low energy inputs. A maximum surface hardness of around 2000 Hv was developed in most of the tracks and this hardness corresponds to high concentration of TiN dendrites within the modified layer.

A Study on the Tensile Property of Jute Yarns Using Weibull Distribution

The characteristics of natural yarns are inconsistent in their mechanical property. The tensile strength of jute yarns is an intricate parameter, which can not be fully described using single value. This necessitates the study of the jute yarn strength distribution and efficient experimental methods for its measurement. Here Weibull model is used to describe the statistical nature of the tensile strength. However, the experimental process widely uses for obtaining the two parameters Weibull model which is described for this experiment. The Weibull modulus of the untreated and NaOH treated jute yarns were determined and it suggests that the treated yarns are better than the untreated yarns. The tensile strength of NaOH treated jute yarns increased to 219.93 MPa compared to the untreated yarns which was 177.32 MPa. For the treated yarns the coefficient value R2 is 0.9829, which indicates good degree of linearity.

Al-4.5 Cu-3.8 Fe In Situ Composites: Effect of Rolling on Microstructure and Wear Properties

Al based MMCs have attracted a lot of attention particularly for their desirable combination of high stiffness and low specific gravity. In the present study, Al-4.5Cu-3.8Fe in-situ composites were manufactured by using solidification process. During solidification Al-Fe intermetallic was formed in a matrix of Al-Cu alloy. The composite was hot rolled at different degree using a two high rolling mill. Subsequently the composites were characterized by SEM, XRD, hardness measurement and wear testing. Wear testing was conducted on a pin-on-disk machine by applying 10 KN load. After the wear tests, the worn surfaces of the composite specimens were examined under an optical microscope. According to experimental results, as cast in-situ composites exhibited the highest wear rate. The hardness increased and wear rate decreased with the extent of rolling. The presence of reinforcing Al3Fe phase and fragmentation of those particles during hot rolling are suggested to contribute to the better wear resistance of the composites. The extent of abrasive wear was largest in the case of as cast composites, as evidenced by deep grooves on the worn surface and highest weight loss.