Brendan Short Brendan Barrett Jason Gamble Engineering 45 SRJC Fall 2011 Sintering Overview What is Sintering How does Sintering Work What Materials can be Sintered What are the advantages of sintering ID: 742927
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Slide1
Sintering of Powdered Copper
Brendan Short, Brendan Barrett, Jason Gamble Engineering 45, SRJC Fall 2011Slide2
Sintering Overview
What is Sintering? How does Sintering Work? What Materials can be Sintered?
What are the advantages of sintering? Slide3
What is Sintering
Sintering is a metallurgical process in which a powdered material is compressed and heated to form a solid part in the desired shape
In more detail:
Solid
state sintering is the process of taking metal in the form of a powder and placing it into a mold or die. Once compacted into the mold the material is placed under a high heat for a long period of time. Under heat, bonding takes place between the porous aggregate particles and once cooled the powder has bonded to form a solid piece.
Sintering can be considered to proceed in three stages. During the first, neck growth proceeds rapidly but powder particles remain discrete. During the second, most densification occurs, the structure recrystallizes and particles diffuse into each other. During the third, isolated pores tend to become spheroidal and densification continues at a much lower rate. The words Solid State in Solid State Sintering simply refer to the state the material is in when it bonds, solid meaning the material was not turned molten to bond together as alloys are formed.[11]
One recently developed technique for high-speed sintering involves passing high electrical current through a powder to preferentially heat the asperities. Most of the energy serves to melt that portion of the compact where migration is desirable for densification; comparatively little energy is absorbed by the bulk materials and forming machinery. Naturally, this technique is not applicable to electrically insulating powders.
To allow efficient stacking of product in the furnace during sintering and prevent parts sticking together, many manufacturers separate ware using Ceramic Powder Separator Sheets. These sheets are available in various materials such as alumina, zirconia and magnesia. They are also available in fine medium and coarse particle sizes. By matching the material and particle size to the ware being sintered, surface damage and contamination can be reduced while maximizing furnace loading.Source: Todd, Robert H., Allen, Dell K., Alting, Leo, "Manufacturing Processes Reference Guide", 1st Edition, Industrial Press Inc., New York 1994, ISBN 0-8311-3049-0Slide4
How Does Sintering Work?
Sintering works by atomic diffusion of powdered materials which is greatly accelerated at high temperatures
In more detail:
Sintering
is a method used to create objects
from powder.
It is based on atomic
diffusion. Diffusion occurs in any material above absolute zero, but it occurs much faster at higher temperatures. In most sintering processes, the powdered material is held in a mold and then heated to a temperature below the melting point. The atoms in the powder particles diffuse across the boundaries of the particles, fusing the particles together and creating one solid piece. Because the sintering temperature does not have to reach the melting point of the material, sintering is often chosen as the shaping process for materials with extremely high melting-points such as tungsten and molybdenum.Source: "Materials Science and Engineering: R: Reports : Consolidation/synthesis of materials by electric current activated/assisted sintering". ScienceDirect. Retrieved 2011-09-30.Slide5
What Can be Sintered?
Most Metals, Ceramics, and Plastics
In more detail:
Most, if not all, metals can be sintered. This applies especially to pure metals produced in vacuum which suffer no surface contamination. Sintering under atmospheric pressure requires the usage of a protective gas, quite often endothermic gas. Many nonmetallic substances also sinter, such as glass, alumina, zirconia, silica, magnesia, lime, ice, beryllium oxide, ferric oxide, and various organic polymers. Sintering, with subsequent reworking, can produce a great range of material properties. Changes in density, alloying, or heat treatments can alter the physical characteristics of various products. For instance, the Young's Modulus
E
n
of sintered iron powders remains insensitive to sintering time, alloying, or particle size in the original powder, but depends upon the density of the final product:
Plastic materials are formed by sintering for applications that require materials of specific porosity. Sintered plastic porous components are used in filtration and to control fluid and gas flows. Sintered plastics are used in applications requiring wicking properties, such as marking pen nibs. Sintered ultra high molecular weight polyethylene materials are used as ski and snowboard base materials. The porous texture allows wax to be retained within the structure of the base material, thus providing a more durable wax coating. Source: "Materials Science and Engineering: R: Reports : Consolidation/synthesis of materials by electric current activated/assisted sintering". ScienceDirect. Retrieved 2011-09-30.Slide6
What are the advantages of Sintering
Very high and uniform purity can be easily achievedThe simple fabrication process retains purity
Grain size is easily controlled
No deformation is needed to produce directional elongation of grains
Void density can be controlled
Objects can be created in any shape
Shapes can be produced that not be made by any other processSlide7
Project Materials and Preparation
99.63% atomized pure copper powder with spherical particles with a range of sizes from 45 to 75 micrometers was usedHydraulic Press
Cylindrical Mold
High Temperature Ovens
Ceramic Oven Cups
Microscope with digital imaging
Polishing and sanding tools
ScaleGloves and protective eyewearBandages for YounesSlide8
Project Procedure
Weigh out 10 gram amounts of copper powder for pellets
Copper powered compressed to cylindrical pellets under 10,000 psi with hydraulic press
Samples put into ovens at temperatures of 900 and 1500 degrees Fahrenheit
Samples pulled from oven at 10 minutes (only 1500 degree), 30 minutes, 60 minutes, 90 minutes (only 900 degree), and 6 hours
Samples sanded, polished, and examined under microscope at 40x lens magnification and 30x camera magnification for around 1200x total magnificationSlide9Slide10Slide11
Project Results:
Photographs of Un-sintered copper pellets
Photographs of 900 degree sintered copper
Photographs of 1500 degree sintered copper
Our Results Clearly show the diffusion of the copper particles over time
Oxidation on a SampleSlide12
Non-Sintered CopperSlide13
Non-Sintered CopperSlide14
900 Degrees for 30 minutesSlide15
900 Degrees for 60 minutesSlide16
900 Degrees for 90 minutesSlide17
900 Degrees for 6 HoursSlide18
1500 Degrees for 10 minSlide19
1500 Degrees for 30 minSlide20
1500 Degrees for 1 hourSlide21
1500 Degrees for 6 hoursSlide22
900 Degree Progression
30 min
60 min
90 min
6
hrSlide23
1500 Degree Progression
1
0 min
30 min
60 min
6
hrSlide24
Expected Results:Slide25
References:
"Materials Science and Engineering: R: Reports : Consolidation/synthesis of materials by electric current activated/assisted sintering"
.
ScienceDirect
. Retrieved 2011-09-30.
Todd, Robert H., Allen, Dell K.,
Alting
, Leo, "Manufacturing Processes Reference Guide", 1st Edition, Industrial Press Inc., New York 1994, ISBN 0-8311-3049-0“The Ultimate Source for Information on Copper and Copper Alloys” http://www.copper.orgMepco (The Metal Powder Company Limited) Materials Safety and Information Sheet