Powder Metallurgy

Experimental Report

Name of University

Supervisor’s

18 December 2019

Contents

Contents 2

Introduction 4

Purpose of the Experiment 4

Problems Being Addressed 5

Scope of the Experiment 5

Test and Evaluation 6

Apparatus Used 6

Process / Procedure / Sequence of Events 6

Findings 11

General 11

Packing Factor 11

Part Packing Factor 11

Porosity 11

Interpretation and Results 13

Conclusions and Recommendations 16

Conclusion of the Experiment 16

Recommendations 21

Appendices 23

Calculations 23

Figures and Tables 24

Figure 1.1: Relationship between Pressure and Green Compact Thickness 24

Table 1.1: Powder Metallurgy Measured Data 25

Presentation of Experiments: Review of Manufacturing Lab Pictures 26

Picture 1.1: Sintered Green Compact 26

Picture 1.2: Non-Sintered Green Compact 26

Picture 1.3: Sintered and Non-Sintered Green Compacts 27

Picture 1.4: Metal Sheet in V-die Bending Machine 27

Picture 1.5: Broken Sintered Green Compact 28

Picture 1.6: Hydraulic Press Machine 28

Picture 1.7: Defects on Broken Sintered Green Compact after Pressure 29

Picture 1.8: Defects on Sintered Green Compact after 70 Tons Pressure Applied on half of The Material 29

Picture 1.9: Bridgeport Vertical Milling Machine 30

Picture 2.1: Little Metal Pieces Gained from Solid Grain Structure 30

Picture 2.2: Metal Pieces Gained from Solid Grain Structure and Powder Metals Gained from Powder Material 30

Picture 2.3: Defects on Sintered Green Compact 31

Picture 2.4: A Penny Placed in Compression Machine 31

Picture 2.5: Defects on Penny after Compression 32

References 33

: Experimental Report

Introduction

Powder metallurgy, or PM, is a process for forming metal parts byheating compacted metal powders to just below their melting points.Although the process has existed for more than 100 years, over thepast quarter century it has become widely recognized as a superiorway of producing high-quality parts for a variety of importantapplications. This success is due to the advantages the processoffers over other metal forming technologies such as forging andmetal casting, advantages in material utilization, shape complexity,near-net shape dimensional control, among others. These, in turn,yield benefits in lower costs and greater versatility.

In reality, PM comprises several different technologies forfabricating semi-dense and fully dense components. The surgicalscissor parts were formed through the metal injection molding (MIM)process, the manifold was manufactured through hot isostatic pressing(HIP), while the connecting rod was produced using powder forging(P/F). Using many of these PM processing techniques, as well as otherprocesses such as spray forming, roll compaction, rapidsolidification, and others, components are also produced today fromparticulate materials other than metal powders. These includecermets, intermetallic compounds, metal matrix composites,nano-structured materials, high-speed steels, to name but a few. [3]

Purposeof the Experiment

By doing this experiment, observing the influences of pressure whencompressing the metal powder into a solid part was aimed. Whenproducing a green compact observing the defects, is one of thepurposes of this experiment too. Moreover, applying many destructivetests on sintered and non sintered parts can taught students whatproblems they can face with when doing powder metallurgy. The lastbut not the least purpose of this experiment is that students willlearn how to do teamwork.

ProblemsBeing Addressed

One of the most general defects on powder metallurgy experiment islamination cracking. Air has not been able to go out from the die,therefore it will be entrapped within the green component. This isgenerally a consequence of trying to press components too fast, andends up with lamination cracking, in a direction perpendicular to thedirection of pressing. It is caused by in inability of adjacentparticles to mechanically interlock due to the layer of compressedair.

Anothermajor defect on powder metallurgy experiment is blowouts. Blowoutsoccur when all the entrapped air tries to go out from a single pointwhere the die and punch meet. [1]

Scope ofthe Experiment

Coverage is broad, encapsulating hard materials, ceramics,composites, and novel materials in addition to metallic particulatematerials, and ranging from the production, handling andcharacterization of powders, through compaction and sintering andother consolidation routes, to the properties, secondary processing,and applications of powder metallurgy components. [2]

Test and EvaluationApparatus Used

  • Bridgeport Vertical Milling Machine

  • Hand Roller

  • Metal Sheet

  • Green Compact Removal Machine

  • Solid Grain Structure

  • Notebook

  • Pen

  • Paper

  • Brass Powder

  • Graduated Cylinder

  • Die Set

  • Dynamic Compression Machine

  • Weight Scale

  • Caliper

  • DakeHydraulic Press Machine

  • Spoon

  • Green Part Extractor

  • Penny

  • 12” Scaled Ruler

  • V-die Bending Machine

Process / Procedure / Sequence of Events

The experiment has taken place for two weeks. In the first week of the experiment, the following steps were done.

  1. Die diameters were measured by the instructor. For die A it was measured as 1.502 inches, for die B the size was measured as 1.505 inches, and for die C the size measured as 1.504 inches.

  2. The cylinder that was graduated was placed on the weight scale.

  3. The graduated cylinder’s weight was measured as 28.2 grams.

  4. To measure the powder weight, the weight scale was set to -28.2 grams.

  5. By using a spoon, brass powder was taken from the bag.

  6. The powder was put into the graduated cylinder.

  7. The brass powder in the graduated cylinder was not enough therefore, more brass powder was put into the cylinder.

  8. The weight of the brass powder was measured as 22.9.

  9. For the first experiment, die B which has 1.504 inches diameter was chosen.

  10. Die B was cleaned by using a dust cloth.

  11. 22.9 grams brass powder was poured into the die set.

  12. Die was placed in the hydraulic press machine.

  13. Press machine’s valve was turned and the machine was prepared.

  14. The die set was placed in the pressing machine.

  15. By using lifter arm, 25 tons pressure was applied to the die set by a student.

  16. After seeing 25 tons by looking the indicator, the valve was turned and the pressure was released.

  17. The die set was removed from the pressing machine.

  18. The die set was placed in the green compact removal machine.

  19. After removing the green compact, it carefully handled by a student

  20. The diameter of the green compact was measured as 1.507 inches.

  21. The thickness of the green compact was measured as 0.126 inches.

  22. Green compact was put on the weight scale.

  23. The weight of the green compact was measured as 22.7 grams.

  24. Die A which has 1.502 inches diameter was chosen.

  25. Die A was cleaned by using a dust cloth.

  26. 22.9 grams brass powder was poured into the die set.

  27. Die was placed in the hydraulic press machine.

  28. Press machine’s valve was turned and the machine was prepared.

  29. The die set was placed in the pressing machine.

  30. By using lifter arm, 30 tons pressure was applied to the die set by a student.

  31. After seeing 30 tons by looking the indicator, the valve was turned and the pressure was released.

  32. The die set was removed from the pressing machine.

  33. The die set was placed in the green compact removal machine.

  34. After removing the green compact, it carefully handled by a student

  35. The diameter of the green compact was measured as 1.504 inches.

  36. The thickness of the green compact was measured as 0.122 inches.

  37. Green compact was put on the weight scale.

  38. The weight of the green compact was measured as 23.3 grams.

  39. Experiment was repeated by applying 35, 40, 45, 50, 55, 60 tons by the students. For each pressure value thicknesses, diameters, and weights for green compacts were measured.

The values were shown in Table 1.1.

For the first week the experiment was completed. All the green compacts were sintered by the instructor until the second week of the experiment. In second week, the following steps were completed:

  1. Differences between sintered and non sintered green compacts were observed as their appearance, hardness, strength, surface condition and size. (Picture 1.3)

  2. To observe its ductility, metal sheet was placed in V-die bending machine, and the metal sheet was bended 90o.

  3. Sintered green compact was placed in the V-die bending machine, and breaking in the green compact was observed.

  4. The process above was repeated two times more with other green compacts, and breaking was observed on all of them.

  5. Another green compact’s thickness was measured as 0.109 inches.

  6. Sintered green compact was placed in the hydraulic pressing machine.

  7. 70 tons of pressure was applied on the green compact.

  8. The thickness of the green compact was measured again, and 0.101 inches were observed.

  9. The green compact which has a thickness of 0.101 inches was placed in V-die bending machine, and breaking on the green compact was observed.

  10. Another sintered green compact was placed in the hydraulic pressing machine.

  11. 70 tons of pressure was applied half of the green compact, and breaking was observed on the green compact.

  12. A solid grain structure that was prepared before by the instructor was placed on Bridgeport vertical milling machine.

  13. The machine was run.

  14. By cutting a part from the solid, little metal chips were gained and observed.

  15. Bridgeport vertical milling machine was stopped.

  16. Solid structure was removed from the machine.

  17. Powder metal structure that was prepared before by the instructor was placed on vertical milling machine.

  18. The machine was run.

  19. By cutting a part from the powder metal structure, little metal pieces were gained and observed.

  20. Both of the object`s metal pieces were observed and compared.

  21. A Canadian coin was placed in the dynamic compression machine.

  22. The machine was run many times by a student, and the defects were observed on the coin.

  23. Another sintered green compact coin was placed in dynamic compression machine.

  24. The machine was run many times by a student, and defects were observed on the sintered green compact.

  25. Two parts were observed together and compared by their defects.

Findings General

  • Flask Weight = 28.2 grams

  • Powder Weights = 22.9 grams

  • Die diameters, part thicknesses, part diameters and part weights are shown in Table 1.1.

  • The thickness of sintered green compact before pressing = 0.109&quot

  • The thickness of sintered green compact after 70 tons pressing = 0.101&quot

Packing Factor

  • PF= Bulk Density / True Density

  • PF= True Specific Volume / Bulk Specific Volume

  • PF= Weight of PM Part / Weight of Solid Part

Part Packing Factor

  • Packing Factor= Volume Weight of Briquette / Volume Weight of Solid

Porosity

  • Porosity + Packing Factor = 1

  • Porosity = 1 – Packing Factor

1)

PF= Powder Weight/ Solid Part Weight

= 22.9 / 22.7=1.008810573

2)

PF= Powder Weight/ Solid Part Weight

=22.9 / 23.3 = 0.982832618

Porosity + 0.982832618 = 1

Porosity = 0.017167382

3)

PF= Powder Weight/ Solid Part Weight

= 22.9 / 23.2 = 0.987068966

Porosity + 0.987068966 = 1

Porosity = 0.012931034

4)

PF= Powder Weight/ Solid Part Weight

= 22.9 / 23.2 = 0.987068966

Porosity + 0.987068966 = 1

Porosity = 0.012931034

5)

PF = Powder Weight / Solid Part Weight

= 22.9 / 23.1 = 0.991341991

Porosity + 0.991341991 = 1

Porosity = 0.008658009

6)

PF= Powder Weight/ Solid Part Weight

= 22.9 / 23.2 = 0.987068966

Porosity + 0.987068966 = 1

Porosity = 0.012931034

7)

PF= Powder Weight/ Solid Part Weight

=22.9 / 23.3 = 0.982832618

Porosity + 0.982832618 = 1

Porosity = 0.017167382

8)

PF= Powder Weight/ Solid Part Weight

=22.9 / 22.9 = 1

Interpretation and Results

The experiment took two weeks to finish. All the measurements for products and the dies are shown in Table 1.1 in the appendix. In first experiment, by using 25 tons of pressure and die B, a green compact was produced. Before producing the compact, 22.9 grams of powder metal was put in the flask, but after producing the green compact the weight was measured as 22.7 grams. That means 0.2 grams of powder metal was lost during the process. After the experiment the measured thickness of the product was 0.126 inches and the diameter was 1.507 inches. Second green compact was produced by using die A and 30 tons of pressure. Before doing the experiment 22.9 grams of powder metal was put in the flask. However, after producing the green compact, the measured weight was 23.3 grams. There was extra 0.4 grams in the product. After the experiment the measured thickness of the product was 0.122 inches and the diameter was 1.504 inches. Third experiment was done by applying 35 tons of pressure and using die C. Before doing the experiment 22.9 grams of powder metal was put in the flask. However, after producing the green compact, the measured weight was 23.2 grams. There was extra 0.3 grams in the product. After the experiment the measured thickness of the product was 0.117 inches and the diameter was 1.505 inches. Fourth experiment was done by applying 40 tons of pressure and using die B. Before doing the experiment 22.9 grams of powder metal was put in the flask. However, after producing the green compact, the measured weight was 23.2 grams. There was extra 0.3 grams in the product. After the experiment the measured thickness of the product was 0.116 inches and the diameter was 1.506 inches.

Fifth experiment was done by applying 45 tons of pressure and using die C. Before doing the experiment 22.9 grams of powder metal was put in the flask. However, after producing the green compact, the measured weight was 23.1 grams. There was extra 0.2 grams in the product. After the experiment the measured thickness of the product was 0.114 inches and the diameter was 1.505 inches. Sixth experiment was done by applying 50 tons of pressure and using die A. Before doing the experiment 22.9 grams of powder metal was put in the flask. However, after producing the green compact, the measured weight was 23.2 grams. There was extra 0.3 grams in the product. After the experiment the measured thickness of the product was 0.112 inches and the diameter was 1.506 inches.

Seventh experiment was done by applying 55 tons of pressure and using die B. Before doing the experiment 22.9 grams of powder metal was put in the flask. However, after producing the green compact, the measured weight was 23.3 grams. There was extra 0.4 grams in the product. After the experiment, the measured thickness of the product was 0.110 inches and the diameter was 1.506 inches. Eighth experiment was done by applying 60 tons of pressure and using die C. Before doing the experiment 22.9 grams of powder metal was put in the flask. However, after producing the green compact, the measured weight was 22.9 grams. In this experiment no error was observed. After the experiment the measured thickness of the product was 0.109 inches and the diameter was 1.505 inches.

The first difference that was observed between sintered and non sintered green compact was the color. Sintered green compact had darker and lackluster color of yellow. However, non sintered green compact had pretty vivid golden color. Other big difference between them was that contrary to sintered one, non sintered green compact was able to break easily. It is because the binder material keeps grains together in sintered green compact. Therefore, sintered green compact was harder to break. Another observation was that surface of sintered green compact was smoother than non-sintered one. After V-die bending machine experiment was done, it was clearer to observe that a powder metal product is more brittle than a solid metal sheet. During the experiment when solid metal sheet was bended 90o, powder metal products were broken. After applying pressure on half of the sintered green compact, a big crack on the midway of the compact was observed. Moreover, there were some other small cracks seen on the green compact. This was caused because of shear effect.

After cutting the solid structure and powder metal material, metal pieces samples were taken and observed. Observation showed that solid structure’s metal pieces were more like spirally and bigger, however, powder metal product’s pieces were like a gold dust. When dynamic compression was applied on the green compact, many small cracks were observed on it. That is because of shear effect too. As the green compact moves between cylinders, there are many shear forces occurs, and they causes many cracks. After that the same process was done for a Canadian coin by a student. Nonetheless, after the experiment was done there was no crack on the coin. The only thing was that there was a big elongation by its size.

Conclusions and Recommendations Conclusion of the Experiment

Following a powder metallurgy process, air may be entrapped within the green component leading to subsequent splintering and cracking of the product mass. Such cracks result either from an air-capsule blowout or from the partial disintegration of components. The process itself may be executed in a manner that allows far too much pressure, too rapid compression rates to formulate layers, and even a mismatch of component states when pressure is applied thus triggering inadequate and unreliable mechanical interlock. Any of these errors often accrues as lamination cracking and sintering of the product. Consequently, and for several decades now, practitioners, scholars, and designers have highlighted the key defect of powder metallurgy processes as lamination cracking, witnessed during the production, handling, and use of powder metallurgy products. Similar negative outcomes have been recorded across a wide range of ceramics, hard materials, composites, and even metallic particulate formulations.

The foregoing eight experiments provided a first-hand exposure to the powder metal processing process, in a manner that validated and or invalidated specific variables to the process with observable indicators. As such, the experiments detailed above were conducted strategically purposed to contextualize, validate, and explore the most significant advantages and disadvantages of the powder metallurgy process. The experiments were implemented to establish the strength of the powder material, if any, explaining why most of experiments conducted were primarily focused on strength indicators including, bending, dynamic compression, pressure and milling properties. The experimentation was purposed to facilitate substantial observation of how pressure influences the materials during the compression of metal powder into solids, while also investigating any significant defects that accrued from the production of the green compact.

Upon conducting the eight experiments, the researcher identified significant green compacts defects that indicated variance in the strength and ductility of the powder metallurgy product. The experimentation experience facilitated the researcher to establish a reliable evidence-based link between the significant defects on the green compact, and the causative conditions/elements/factors including material tolerance levels and certain design considerations (i.e. material weight, thickness and, diameter). A minor change in the material features ultimately (i.e. weight or thickness) and significantly influenced variations in powder material’s pressure.

At the onset of the eight experiments, the researcher merely held theoretical assumptions that lacked practical credence and reliability. For instance, based on theoretical assumptions, it was predictably that, wrongful and repetitive application of destructive tests on sintered and non-sintered parts was likely to yield negative outcomes during powder metallurgy. The experiments however not only conformed and validated this assumption, but further provided sustainable learning experiences for the researcher, particularly when characterizing such consolidation routes and routines as compaction, and processing versus the realities of powder metallurgy. The experiments enabled the researcher to understand certain powder metal properties that may vary by parts including brittlelity, understand how design variation influenced the outcomes of powder metallurgy, and even contextualize the role of a binder material when containing powder metals. Ultimately, the experimentation also provided additional benefits of learning to build, sustain, and improve teamwork.

Recommendations

Based on the foregoing results, interpretation, and conclusion of the experiments, several issues emerge to justify a significant recommendation for practice of and future research on powder metallurgy. To begin with, the researcher recommends careful, precise, and strategic handling of the precious metal powders during processing. How materials are measured and balanced has a significant influence on the process, for even the slightest measurement variations triggers significant impact on the diameters, weight, and thickness of the materials. When not mitigated, such variations may not only compromise on the quality and value of the product, but also on its usability thereafter. Further, without such care, losses may eventually become unsustainable and regrettable, besides jeopardizing the quality outcomes of a powder metallurgy process. When conducting the experiment, the researcher witnessed a moment when the powder metal was handled carelessly, when removing the green compact from the machine. Upon dropping, the powder metal became unusable

Appendices

Calculations

Part Volume =

Part Volume 1 = 0.224743392

Part Volume 2 = 0.216743152

Part Volume 3 = 0.208136738

Part Volume 4 = 0.206632112

Part Volume 5 = 0.202799898

Part Volume 6 = 0.199506867

Part Volume 7 = 0.195944244

Part Volume 8 = 0.193905166

Packing Factor = PF = =

Porosity = 1 – PF

PF 1 = 1.008810573 Porosity 1 = -0.008810573

PF 2 = 0.982832618 Porosity 2 = 0.017167382

PF 3 = 0.987068966 Porosity 3 = 0.012931034

PF 4 = 0.987068966 Porosity 4 = 0.012931034

PF 5 = 0.991341991 Porosity 5 = 0.008658009

PF 6 = 0.987068966 Porosity 6 = 0.012931034

PF 7 = 0.982832618 Porosity 7 = 0.017167382

PF 8 = 1 Porosity 8 = 0

Figures and Tables

Figure 1.1: Relationship between Pressure and Green Compact Thickness

Relationship between Pressure and Green Compact Thickness

Table 1.1: Measured Data

DIE

DIE I. D

TONS

POWDER WEIGHT

PART THICKNESS

PART DIAMETER

PART WEIGHT

B

1.505&quot

25

22.9

0.126

1.507

22.7

A

1.502&quot

30

22.9

0.122

1.504

23.3

C

1.504&quot

35

22.9

0.117

1.505

23.2

B

1.505&quot

40

22.9

0.116

1.506

23.2

C

1.504&quot

45

22.9

0.114

1.505

23.1

A

1.502&quot

50

22.9

0.112

1.506

23.2

B

1.505&quot

55

22.9

0.11

1.506

23.3

C

1.504&quot

60

22.9

0.109

1.505

22.9

Measured Data

Presentation of Experiments: Review of Manufacturing Lab Pictures

Picture 1.1: Sintered Green Compact

Picture 1.2: Non-Sintered Green Compact

Picture 1.3: Sintered and Non-Sintered Green Compacts

Picture 1.4: Metal Sheet in V-die Bending Machine

Picture 1.5: Broken Sintered Green Compact

Picture 1.6: Hydraulic Press Machine

Picture 1.7: Defects on Broken Sintered Green Compact after Pressure

Picture 1.8: Defects on Sintered Green Compact after 70 Tons Pressure Applied on half of The Material

Picture 1.9: Bridgeport Vertical Milling Machine

Picture 2.1: Little Metal Pieces Gained from Solid Grain Structure

Picture 2.2: Metal Pieces Gained from Solid Grain Structure and Powder Metals Gained from Powder Material

Picture 2.3: Defects on Sintered Green Compact

Picture 2.4: A Penny Placed in Compression Machine

Picture 2.5: Defects on Penny after Compression

References

[1] http://www.azom.com/Details.asp?ArticleID=1415

[2] Maney Publishing, http://www.scimagojr.com/journalsearch.php?q=27885&amptip=sid

[3] Texas A&ampM University, http://www.materialseducation.org/educators/new/2006/docs/Griffin%20Paper%20Exp%20In%20PM06_08-11-06.pdf

[4] Pictures from Manufacturing Lab Section 01