PHYSICAL BEHAVIOUR OF POWDER CERAMIC PART USING
COLD ISOSTATIC PRESSING (CIP) PROCESSES
SARIZAL BIN MD. ANI
A project report submitted in partial fulfilment of the requirement
for the award of the degree of Master of Engineering
(Mechanical-Advanced Manufacturing Technology)
Faculty of Mechanical Engineering
Universiti Teknologi Malaysia
Kepada isteri saya yang disayangi: Wan Noor Azna Binti Abdul Rahim Anak saya: Siti Syazwani
Kedua ibubapa saya: Md. Ani Bin Ahmad dan Zaiton Binti Ahmad Kawan-kawan saya
TERIMA KASIH atas segala jasa dan sokongan yang telah diberikan
ACKNOWLEDGENT
I would like to express my sincere appreciation to my supervisor Assoc. Prof. Dr. Safian Sharif for his guidance, encouragement and patience throughout this master project. I also would like to thank to UTM lecturer, Japan-Malaysia Technical Institute staff and who have contributed to the success of this project.
ABSTRAK
Proses Penekanan Sestatik Sejuk (CIP) digunakan secara meluas bagi tujuan pra-pembentukan serbuk sebelum penumpatan selanjutnya melalui proses pensinteran. Penekanan sestatik boleh menghasilkan tekanan yang tinggi secara seragam melalui semua arah komponen produk di mana kepadatan adalah konsisten bagi seluruh keratan dan ketepatan yang tinggi berbanding dengan penekanan searah. Hal yang demikian akan menghasilkan penumpatan yang lebih seragam dan pemadatan yang sangat baik. Melalui kajian ini kesan parameter CIP terhadap kelakuan pengecutan, kekerasan dan ketumpatan bagi serbuk alumina akan dapat diketahui. Kesan suhu pensinteran terhadap kebulatan, kesilinderan dan kekasaran permukaan bagi bahagian seramik juga akan dapat diperolehi. Melalui kajian ini juga hubungan di antara parameter proses dan tindakbalas proses bagi bahan alumina akan dapat ditentukan di mana keputusan yang diperolehi boleh digunakan bagi menghasilkan produk yang hampir kepada bentuk pembuatannya.
ABSTRACT
Cold Isostatic Press (CIP) is mainly used for pre-forming of powder parts prior to a further densification by sintering. Isostatic pressing can apply very high pressure uniformly in all directions producing parts, which are consistent in density throughout their cross sections and highly accurate as compared to those produced uniaxially. This results in more uniform density and greater compaction. In this study the effect of CIP parameters on the shrinkage, hardness and densification behaviour of the alumina oxide powder are examined. The effect of sintering temperature on the roundness, cylindricity and surface roughness of the ceramic parts are also investigated. As a result of this study the relationship between the process parameters and the responses of alumina powder were established and can be used to produce product with the near net shape manufacturing.
CONTENTS
CHAPTER TOPIC PAGE
TITLE i
DECLARATION ii
DEDICATION iii
ACKNOWLEDGENT iv
ABSTRAK v
ABSTRACT vi
CONTENTS vii
LIST OF TABLES xi
LIST OF FIGURES xii
LIST OF APPENDICES xv
1 INTRODUCTION 1
1.1 General Background 1
1.2 Problem Statement 2
1.2.1 Mechanical Properties 1.2.2 Geometrical Dimensioning Tolerance (GDT) 3
1.3 Objective 4
1.4 Scope of the Project 4
1.5 Expected Results 5
2 LITERATURE REVIEW 6
2.1 Introduction 6
2.2 Cold Isostatic Press (CIP) 6 2.2.1 Type of Cold Isostatic Press (CIP) 8 2.2.2 Cold Isostatic Press (CIP) Processes 8 2.3.3 Cold Isostatic Press (CIP) Chamber Pressure 10 2.3.4 Cold Isostatic Press (CIP) Technology
Application 12
2.3 Ceramic Processing 13
2.3.1 Raw Materials: Crushing and Additives 14
2.3.2 Shaping Ceramics 14
2.3.3 Drying 16
2.4.4 Sintering 16
2.4.5 Finishing 17
2.4 Ceramics 18
2.4.1 Properties of Ceramics 19
2.4.2 Applications of Ceramics 21
2.5 Alumina Powder 22
2.5.1 Properties of Alumina Powder 24
2.6 Rubber Mold 26
2.6.1 Hardness of Rubber Mold 28 2.7 CIP Process on Alumina Powder 28
2.7.1 Alumina Powder 32
3 METHODOLOGY 36
3.1 Introduction 36
3.2 Project Methodology 37
3.3 Experimental Matrix 38
3.4 Experimental Procedures 40
3.4.1 Alumina Powder 43
3.4.2 Cold Isostatic Press (CIP) Machine 43
3.4.3 Rubber Mold 45
3.4.4 Sintering Furnace 46
3.5 Measurement of The Responses 46
3.5.1 Hardness Measurement 47
3.5.2 Density Measurement 47
3.5.3 Shrinkage and Geometrical Dimensioning
Tolerance (GDT) Measurement 48
4 RESULTS AND DISCUSSION 49
4.1 Introduction 49
4.2 Hardness 50
4.3 Green Density (Before Sintering) 53 4.4 Density After Sintering Process 55 4.5 Shrinkage of the Green Compact 61 4.6 Shrinkage After Sintering 65 4.7 Geometrical Dimensioning and Tolerancing (GDT):
Roundness and Cylindricity 71
4.8 Surface Roughness 78
5 CONCLUSION 82
REFERENCES 85
APPENDICES A-D 89
LIST OF TABLES
TABLE NO. TITLE PAGE
2.1 Characteristics of ceramics processing 15 2.2 Properties of various ceramics at room temperature 20 2.3 Types and general characteristics of ceramics 21 2.4 Detailed specification of alumina powder 25 2.5 Properties of polyurethane 27 2.6 Operating pressure guidelines for various powders 29 3.1 Selected process parameters and numbers of levels 38 3.2 Pressing pressure 100 MPa with pressing time and sintering
temperature 38
3.3 Pressing pressure 150 MPa with pressing time and sintering
temperature 39
3.4 Pressing pressure 200 MPa with pressing time and sintering
temperature 39
3.5 Chemical composition of alumina A-96 43 3.6 Detailed specification of cold isostatic press (CIP) machine 44 4.1 Frequency of sample base on roundness range 74 4.2 Frequency of sample base on cylindricity range 77
LIST OF FIGURES
FIGURE NO. TITLE PAGE
2.1 Isostatic vs uniaxial 7
2.2 Isostatic shape change 7
2.3 Wet bag isostatic pressing 9 2.4 Dry bag isostatic pressing 9 2.5 Full threaded ASME cover 10
2.6 Breech lock ASME cover 11
2.7 Pin closure ASME cover 11
2.8 Processing steps involved in making ceramic parts 13 2.9 Micrograph of alumina powder 22
2.10 Rubber mold sample 26
2.11 Durometer scale 28
3.1 Wet bag cold isostatic presss machine 44 3.2 Dimensions of the rubber mold 45 4.1 Hardness of sintered alumina powder at various pressing pressure 51 4.2 Hardness of sintered alumina powder at various pressing time 51 4.3 Hardness of sintered alumina powder at various sintering
temperature 52
4.4 Density (green) of alumina powder at various pressing pressure 54 4.5 Density (green) of alumina powder at various pressing time 54 4.6 Density of sintered alumina powder at various pressing
pressure 56
4.7 Density of sintered alumina powder at various pressing time 57 4.8 Density of sintered alumina powder at various sintering
temperature 58
4.9 Densification of alumina powder between green and
sintered at 100 MPa 59
4.10 Densification of alumina powder between green and
sintered at 150 MPa 60
4.11 Densification of alumina powder between green and
sintered at 200 MPa 60
4.12 Green shrinkage (diameter & height) of alumina powder
at various pressing pressure 62 4.13 Green shrinkage (diameter & height) of alumina powder
at various pressing time 63
4.14 Green shrinkage of alumina powder between
diameter and height at 100 MPa 64 4.15 Green shrinkage of alumina powder between
diameter and height at 150 MPa 64 4.16 Green shrinkage of alumina powder between
diameter and height at 200 MPa 65 4.17 Shrinkage after sintered (diameter & height) of alumina powder
at various pressing pressure 66 4.18 Shrinkage after sintered (diameter & height) of alumina powder
at various pressing time 67
4.19 Shrinkage after sintered (diameter & height) of alumina powder
at various sintering temperature 68 4.20 Sintered shrinkage of alumina powder between
diameter and height at 100 MPa 69 4.21 Sintered shrinkage of alumina powder between
diameter and height at 150 MPa 70 4.22 Sintered shrinkage of alumina powder between
diameter and height at 200 MPa 70
4.23 Specifying roundness 71
4.24 Roundness of alumina powder at various pressing pressure 72 4.25 Roundness of alumina powder at various pressing time 72 4.26 Roundness of alumina powder at various sintering temperature 73
4.27 Specifying cylindricity 74 4.28 Cylindricity of alumina powder at various pressing pressure 75
4.29 Cylindricity of alumina powder at various pressing time 76 4.30 Cylindricity of alumina powder at various sintering temperature 76 4.31 Specifying surface roughness 78 4.32 Surface roughness of alumina powder at various
pressing pressure 79
4.33 Surface roughness of alumina powder at various pressing time 80 4.34 Surface roughness of alumina powder at various sintering
temperature 80
LIST OF APPENDICES
APPENDIX NO. TITLE
A Result of Experiment
B Result of Experiment (Raw Data) C Sources of Data for Analysis D Equipment Specification
CHAPTER 1
INTRODUCTION
1.1 General Background
Isostatic presses are used for many applications ranging from casting repair to ceramic ball bearings. The process can be cold, warm or hot to accomplish the desired task. Cold Isostatic Press (CIP) are used mainly for pre-forming of powder prior to further densification by sintering. CIP come in two types; wet bag and dry bag.
In a wet bag CIP the pressure container is full of water and the rubber bag (mold) is removed after each cycle and refilled. This type of press is common when large, complex or many different parts are required. The main benefit of isostatic pressing is uniform density, which results in predictable and repeatable shrinkage upon sintering [1].
This project is undertaken with the aims in understanding the effect of CIP and sintering process on the physical behaviour of powder ceramic part with respect to shrinkage, hardness, density, roundness, cylindricity and surface roughness.
1.2 Problem Statement
Cold Isostatic Press (CIP) process involved various parameters such as pressing pressure, pressing time and grain size of the ceramic powders. These parameters significantly affect the mechanical and physical properties of the ‘green’ or ‘as-pressed’ compact before and after sintering process such as density, hardness, strengthness and dimensional accuracy. In this study, the effect of the CIP parameters on shrinkage, hardness, roundness, cylindricity, surface roughness and densification behaviour of the ceramic powder will be examined. Eventually the results obtained will be used to design and produce a more accurate mold in complying with the near net shape manufacturing.
1.2.1 Mechanical Properties
Compared to metals, ceramics have the following relative characteristics: brittleness; high strength and hardness at elevated temperatures; high elastic modulus; and low toughness, density, thermal expansion, and thermal and electrical conductivity [2]. However, because of the wide variety of ceramics material composition and grain sizes, the mechanical and physical properties of ceramics vary significantly.
Because of their sensitivity to flaws, defects, and surface or internal cracks, the presence of different types and level of impurities, and different methods of manufacturing, ceramics can have a wide range of properties [3]. For Cold Isostatic Press (CIP) processes, mechanical properties of ceramic depend on the pressing pressure and pressing time process parameters. The relationship between these process parameters will be studied to determine the hardness and density of alumina powder after compaction and sintering processes.
1.2.2 Geometrical Dimensioning Tolerance (GDT)
The sintering process causes merging of the particles by diffusion. This mechanism causes the powder particles to move a little closer and therefore some amount of shrinking occurs in the size of the green compact. If the shrinkage is non-uniform or if some dimensions are critical, then the sintered part must be subjected to finishing operations to maintain its specification [4].
The main benefit of CIP process is uniform density, which results in predictable and repeatable shrinkage upon sintering. The fluid pressure acts uniformly in all direction, therefore no die to control shape but must understand shrinkage relationships [4]. By CIP processes geometrical dimensioning tolerance, surface roughness and shrinkage of ceramic maybe depend on pressing pressure and pressing time or sintering temperature process parameters. The relationship between these process parameters will be studied to determine roundness, cylindricity and shrinkage of alumina powder after sintering.
1.3 Objective
Two specific objectives have been defined to simplify the main objective of the project. There are:
1. To study the effect of CIP parameters on the shrinkage, hardness and densification behaviour of the green compact of alumina.
2. To investigate the effect of sintering temperature on the roundness, cylindricity and surface roughness of the ceramic part.
1.4 Scope of the Project
The scopes of the project are as follows:
1. Cold Isostatic Press (CIP) process and sintering process will be employed in producing the ceramic part.
2. The material used for the compaction and sintering process is Aluminium Oxide (Al2O3).
3. Input parameters to be used included are pressing pressure, pressing time and sintering temperature.
4. Output responses to be investigated include shrinkage, hardness, density, roundness, cylindricity and surface roughness.
1.5 Expected Results
This project attempts to evaluate the effect of the pressing pressure and pressing time of Cold Isostatic Press (CIP) process and sintering temperature in order to obtain good physical behaviours (hardness and density) and dimensional accuracy of the ceramic part. Based on the literature review and suppliers recommendations, the following results are expected:
1. The relationship between the process parameters and the responses of alumina powder will be established.
2. The acceptable process parameters for producing the appropriate responses of alumina powder will be determined.
3. The predicted results and repeatable shrinkage upon sintering will be used for designing the rubber mold, to achieve a near net shape product.
4. The result of physical behaviours (hardness and density) will be used for determine the suitable function and application.
5. An accuracy within ±0.7mm is expected through the GDT analysis.