Study of Graphite Content and Sintering Temperature on Microstructure Properties of Iron-Based Powder Preform (original) (raw)
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Global Journal of Research In Engineering, 2014
In this present work effect of temperature and graphite contents on the microstructural and mechanical properties of iron based powder metallurgy freeform was studied. The different graphite (carbon 98%) contents (0%, 2%, 5% and 10%) were mixed in iron powder and compact them in 100 KN. These specimens were sintered at 700⁰ C, 850⁰ C and 1000⁰ C in muffle furnaces. Microstructural properties were evaluated using scanning electron microscopy. Experimental results were compared to determine to best combination of graphite and iron powder preform. Maximum density was found between the range 2% to 5% graphite contents and temperature at 850⁰C. At graphite contents increases from 0% to 2%, the microstructure of the iron-based powder sintered specimen changes gradually from ferrite and a small amount of pearlite to pearlite, after 2% of graphite contents the microstructure was found pearlite and ferrite. As graphite increase up to 5% gray cast iron structure and at 1000⁰ C temperature ran...
Global Journal of Research In Engineering, 2014
The present paper investigates the effect of sintering temperature and graphite content on the microstructure and effect on wear and frictional properties of Fe+C powder metallurgy preforms. For the present work the specimens were prepared with graphite content 0.5%, 1%, 1.5% and 2% by weight and were sintered at three sintering temperature 800°C, 900°C and 1050°C. Microstructural properties were evaluated using scanning electron microscopy. The wear and friction property of the powder preforms were tested on Pin-On-Disc apparatus. The powder specimen was used as pins and the disc was of AISI 51200 steel. The experiments was carried out under load of 40 N, speed 1000 rpm, time 1500 seconds and relative humidity 60% 65%. The result was 2% graphite content specimen with sintering temperature 1050°C showed good wear resistance. The wear rate decreased with the increase in sintering temperature and increase in graphite content of the specimen.
Archives of Metallurgy and Materials, 2019
The paper presents the effect of manganese on the crystallization process, microstructure and selected properties: cast iron hardness as well as ferrite and pearlite microhardness. The compacted graphite was obtained by Inmold technology. The lack of significant effect on the temperature of the eutectic transformation was demonstrated. On the other hand, a significant reduction in the eutectoid transformation temperature with increasing manganese concentration has been shown. The effect of manganese on microstructure of cast iron with compacted graphite considering casting wall thickness was investigated and described. The nomograms describing the microstructure of compacted graphite iron versus manganese concentration were developed. The effect of manganese on the hardness of cast iron and microhardness of ferrite and pearlite were given.
Direct laser sintering of iron–graphite powder mixture
Materials Science and Engineering: A, 2004
In the present work, the role of graphite addition on the laser sintering of iron powder was studied. Powder mixtures containing iron and 0.4, 0.8, 1.2, and 1.6 wt.% graphite were prepared by blending elemental powders. These powders were sintered layer-by-layer under nitrogen atmosphere using a continuous wave CO 2 laser beam. A laser power of 70-225 W, scan rate of 50-600 mm s −1 , scan line spacing of 0.1-0.3 mm, and layer thickness of 0.1 mm was used. It was found that the processing parameters play a key role on the densification of the iron-graphite powder mixtures. The addition of graphite enhances the densification of the iron powder and improves the surface quality of the laser sintered parts when optimized manufacturing conditions are applied. The graphite content has a significant influence on the internal pore structure of the sintered parts. They are gradually changed from interconnected networks to closed and spherical shaped pores with increasing graphite content. The metal matrix structure consists of different phases such as ferrite, austenite, and tempered martensite, which highlights the heterogeneous distribution of dissolved carbon in the iron matrix. This article presents the experimental details of the microstructural evolution in laser sintered iron-graphite powder mixtures. The role and key importance of graphite addition to iron powder in the laser sintering process is addressed.
Journal of Materials Research and Technology, 2018
The effect of holding time, thickness and annealing heat treatment on the microstructure and some mechanical properties of compacted graphite iron (CGI) are studied. Samples of CGI are produced in Helwan factory for casting by using GGG 70 as base metal in a medium frequency induction furnace. The mechanical properties (tensile strength, and hardness) of the as-cast and after heat treatment samples are determined and the microstructure of the samples is examined using optical microscope. The results show that the mechanical properties and microstructure of CGI depend on holding time, thickness and annealing heat treatment; it is found that increasing the holding time from 10 min to 17 min results in lowering the Mg content from 0.031% to 0.021% and as a result lower nodularity was obtained. Lowering the thickness from 20 mm to 5 mm increases the tendency of dendritic structure as a result of increasing the cooling rate. The annealed samples with mainly ferritic matrix gave the lowest tensile strength and hardness value compared with the as-cast conditions.
METAL 2020 Conference Proeedings, 2020
The subject of this article is the failed bushing used in the car suspension. The claim of the broken bushing came from the car producer. The main aim of this paper was to know if the failure was a green crack as evidenced by steam treatment oxide on the crack interfaces. To check, these items a Scanning Electron Microscope (SEM), hardness testers, and optical microscope were used. The density of the upper edge where the crack occurred was checked. Based on this investigation it was found that the crack was not caused by the rollover application.
The ever-increasing development of applying the iron pieces made by powder metallurgy in car industries and other usages depends on making pieces with high density and consequently acceptable physical and mechanical properties. Regarding the effect of decrease in the powder bits' size on improvement of the mechanical characteristics and on decrease in the temperature of sinter, the experiments on the pure iron powder with the bits' size of 5, 45, 63 micron in which 20% of iron nanopowder was added to the powder with the bits' size of 45 micron, have been studied. Mere iron nanopowder also was applied for experiments. Pieces are compacted under 300-850 MPa and lubricants by0.4 and 0.6 percent of the total weight was mixed with the powders. Various amounts of sintering time and sintering temperature were considered for the sintering of the samples. The survey suggested that applying micro powders resulted in an increase in the linear density and the strength at the relatively high temperatures and high keeping times. Sintering temperature and shrinkage has declined considerably with the decrease in the powder size and as a result the strength increases. High strength for products made by smaller powders under high pressures and low sintering temperatures using lubricated frame wall are obtained. SEM pictures from the fracture junctions of the samples show the decrease in porosity due to the close impact of the smaller powder size.
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006
The effect of graphite nodularity on microstructure and processing window of austempered cast iron with four-different levels of graphite nodularity and a composition of 3.6% C, 2.2% Si, 0.2% Mn, 1.5% Ni, 0.3% Mo was studied. Microstructural observations and measurements of the retained austenite content and hardness, are reported as functions of austempering time at 440 and 300 • C after austenitising at 900 • C. The results of the experimental investigation indicate that graphite nodularity has considerable effect on the microstructure. After 8 min austempering time at 440 • C austempering temperature and 20 min austempering time at 300 • C austempering temperature, the amount of retained austenite (X␥) increases with the graphite nodularity. The microstructural investigation and hardness test investigation indicate that the graphite nodularity has a significant effect on the time t 1 corresponding to the end of stage I (process window), whereas decreasing the graphite nodularity delays the end of stage I reaction. The starting time of reaction II, t 2 is determined from the variation of X␥ with austempering time, it is indicated that lower graphite nodularity accelerates the start of stage II reaction.
Journal of Alloys and Compounds, 2009
This paper investigates various methods of producing compacted graphite iron (CGI). The process parameters affecting the mechanical properties and microstructures of CGI were studied. These parameters include the chemical composition, holding time, temperature and thickness of the casting. The results indicated that the nodularity increased with increasing percentage of residual Mg, whereas increasing the Cu content was found to sharply increase the amount of pearlite within the CGI. The amount of Mg decreased with excessive hold times and the optimum was found to be approximately 4 min for producing casts containing between 0.008% and 0.012% residual Mg. Increasing the temperature resulted in some loss or fading in the Mg content and increasing the casting thickness resulted in a decrease in the nodularity. In terms of the mechanical properties, both the tensile strength and hardness were found to increase with increasing residual Mg content and nodularity. Empirical equations were proposed to indicate a relation between the nodularity (%), the residual Mg (%) and other parameters.