Abstract: The importance of medium carbon steels as engineering materials is reflected by the fact that out of the vast majority of engineering grade ferrous alloys available and used in the market today, a large proportion of them are from the family of medium carbon steels. Typically medium carbon steels have a carbon range of 0.25 to 0.65% by weight, and a manganese content ranging from 0.060 to 1.65% by weight. Medium carbon steels are more resistive to cutting, welding and forming as compared to low carbon steels. From the last two decades a number of research scholars reported the use of veritiy of heat treatments to tailor the properties of medium carbon steels. Spheroidising is the novel industrial heat treatment employed to improve formability and machinability of medium/high carbon low alloy steels. This exclusive study covers procedure, the effects and possible outcomes of various heat treatments on medium carbon steels. The austenite phase present in steel above the critical temperature has the tendency to form variety of non equilibrium phases depending upon the degree of supercooling or cooling rates. The near spherical or curved shaped carbides records least resistance for machining because the blunt cornered shapes are having least free energy with minimum internal stresses. There is a need to formulate the heat treatment process to tailor the characteristics in line with the application. The age old normalizing treatment provides more nucleation sites required for so that finer spheroids are dispersed in the matrix to improve toughness with balanced bulk hardness related properties to improve machinability. In line with requirements, the heat treatment cycle to balance mechanical and microstructural properties of AISI 1040 structural steel is designed. It is observed that lower spheroidizing temperature gives finer spheroids, more in number with better improvement in toughness whereas higher Spheroidization temperature reduces hardness values with lesser spheroid density, accordingly reduces strength and impact resistance. The balanced improvement in properties may be incorporated for metal removal operations to improve productivity and tool life.
Abstract: This research aims to investigate the effect on tensile strength of the recycled chip AA6061 aluminium alloy metal by using powder metallurgy method. Material used is recycled aluminium Chip AA6061 and Al powder. The recycled AA6061 chips mixed together with various compositions of Al powder content were fabricated to form a specimen by hot compaction technique. The compaction using hot pressed at 30 tons with holding time of 60 minutes. The final product was analyzed by tensile test shown the specimen A5 have higher ultimate tensile strength (UTS) 156.404 MPa and yield strength (YS) at 107.399 MPa. Scanning Electron Microscopy (SEM) was conducted to observe the microstructure of fracture surface existing on the tensile specimens.
Abstract: The present study is aimed at investigating wear resistance of the heat treated of recycled aluminium type AA6061 for various reinforced methods (heat treatment reinforced by graphite and silica) using pin on disc method. In the study, weight loss value of the recycled chip of AA6061 was observed. Eight specimens were taken for the wear test. The results showed that the wear resistance increased for specimens treated by heat treatment. This increase in wear resistance is value of micro hardness which increased with the increase of the percentage of silica reinforcement. Thus, the weight loss decreased and the volume loss also decreased.
Abstract: Boron alloyed steels, especially 22MnB5, have been the point of focus for the materials choice in hot stamping. Objective of this project is to analyze the effect of heat treatment on its flexural performance. In this paper, five conditions of boron steels are analyzed. Specimens consist of the as-received (A), hot pressed (H) and quenched boron steel (QA,QWR, QWC). Flexural test was conducted to give more evidence on the flexural strength of the boron steel based on their process of heat treatment. Result show that Boron steel 22MnB5 undergone quenching process by using water at room temperature yield highest flexural strain.
Abstract: Aluminium is ranked after iron and steel in the metal market. Aluminium 6061 alloy has been selected by many designers and engineers for different kind of applications. Further, its strength can be improved by cold working, refinement of grains, precipitation and dispersion hardening. In this work, trials are conducted for the investigation of the effects due to age hardening parameters like, solutionizing time, temperature and time for aging on hardness of 6061 Aluminium alloy using Design of Experiments. The response is predicted by using linier regression model. From the results it can be perceived that, the ageing temperature and aging time have a substantial effect on the response whereas, solutionizing time does not have a significant effect. For a specific set of parameters the hardness is improved from 50 to 74 BHN, resulted in an increase in hardness by about 50%.
Abstract: Due to high content of carbon and poor weldability, the ultrasonic frequency induction cladding technique was utilized to fabricate Ni-based alloy coating on the substrate of gray cast irons. In order to investigate the microstructure and properties of Ni-based alloy coating, the techniques of optical microscopy (OM), backscattered electron image (BEI), X-ray diffraction (XRD) and Vickers microhardness tester were employed. And then the immersion test and potentiodynamic polarization measurement were performed to evaluate the corrosion behavior of Ni-based alloy coating. The experimental results reveal that the coating bonds metallurgically with the substrate. Due to the elemental interdiffusion between the coating and the substrate, a solid solution zone of coating is formed. The phases of γ-Ni, Ni3B, NiSi, chromium borides and carbides can be distinguished in the coating. Chromium borides and carbides are benefit for the improvement of hardness and NiSi provides good corrosion resistance.
Abstract: Microstructure and mechanical properties of equiatomic CrMnCoNiCu alloy in which Fe was substituted by Cu from Cantor alloy was studied. The separation of solid solution phase into two solid solutions (Cr-Co rich and Cu-rich phases) were observed in CrMnCoNiCu. The coarsening and widening of interdendritic Cu-rich phase after homogenization was observed and supported by the increase of XRD peak height from Cu-rich phase compared to that from Cr-Co rich phase after homogenization. The increase of the peak from Cu-rich phase can be attributed to the thermodynamic stability of Cu due to positive mixing enthalpy of adding Cu. The stress-strain curves of CrMnCoNiCu alloy exhibited the reasonably high strength and excellent deformability for the cast alloy. The yield stress of CrMnCoNiCu was observed to be 390MPa and it could be deformed without crack formation up to the true strain 0.85 to reach the flow stress as high as 662Mpa.
Abstract: Acicular ferrite (AF) and upper bainite (UB) are microstructural constituents commonly found in ferritic weld metals. Both microstructures are formed within a similar temperature range and by the same type of transformation mechanisms. They have however, substantially different morphologies and microstructural features that govern both their mechanical properties and hydrogen embrittlement susceptibility. This work shows that despite substantial microstructural differences, the mechanical properties of both microstructural constituents were quite similar. However, the microstructural differences were found to significantly affect the hydrogen crack propagation resistance. Hydrogen assisted cold cracking (HACC) propagates along a path of least resistance through the surrounding microstructure. The unit crack path was significantly shorter for AF than for UB, which implied more frequent changes in direction and thus increased dissipation of energy from the crack driving force. These results suggest that AF, possessing fine interlocking grains and high angle grain boundaries (HAGB), increases the localised resistance to HACC propagation more than UB due to the impediment of brittle, cleavage-like crack propagation at HAGB’s.
Abstract: In this paper, a series of milling tests were carried out in order to identify the effects of variable pitch on cutting temperature, cutting force and surface roughness while end milling the stainless steel 316L using Nitico30 and conventional cutting tools. Slot-milling operations were conducted. The value of feed rate were choose between the range recommended by the manufactured for the both conventional and Nitico30 cutting tool. The effect of variable pitch on cutting temperature, cutting forces and surface roughness were discussed. Results showed that the cutting temperature increase with the increase of feed rate for both cutting tool. Further increasing the speed of feed rate, the cutting forces also gradually increase for both cutting tool. However, the comparison between both cutting tools, it was found that the cutting temperature, cutting force and surface roughness improve about 47.8%, 37.5% and 17.6% respectively for Nitico30 cutting tool.