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3.6 Schematic diagram of superplastic boronizing clamp 38

3.7 Dimension of the upper block for superplastic boronizing clamp:

(a) top view (b) front view 39

3.8 Dimension of the lower block for superplastic boronizing clamp:a) top view (b) front view 39

3.9 Superplastic boronizing clamp:

(a) clamps components (b) ready to use clamp 40

3.10 Schematic diagram of superplastic boronizing specimen inside the clamp 41

3.11 Illustration of superplastic boronizing process 42

3.12 Distance between screws and specimen 45

3.13 Free body diagram of upper block 46

3.14 Free body diagram of the specimen 46

3.15 (a) Front view and top view of fabricated die 48

(b) Fabricated upper jig and lower jig 48

3.16 Instron machine used to compressed specimen 49

3.17 Experimental set-up for superplastic deformation test 50

3.18 Process diagram of superplastic deformation testing 50

3.19 X-ray diffraction analysis machine 53

3.20 XRD chamber where samples are subjected to X-rays at different angles 53

3.21 Optical microscope with image analyzer system 54

3.22 Scanning electron microscope (SEM) 55

3.23 Microscope chamber of the SEM where the samples are placed for

analysis 55

3.24 Microhardness tester 56

4.1 (a) Optical image of as-received DSS 57

(b) SEM image of as-received DSS 57

4.2 (a) Optical image of fine microstructure DSS 58

(b) SEM image of fine microstructure DSS 58

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4.3 (a) XRD pattern of specimen before and after boronizing for fine

microstructure DSS 59

(b) XRD pattern of specimen before and after boronizing for

as-received DSS 59

4.4 (a) Rougness profile of DSS for 100-grit 60

(b) Rougness profile of DSS for 240-grit 61(c) Rougness profile of DSS for 600-grit 61

(d) Rougness profile of DSS for 1200-grit 61

4.5 (a) SEM images of Ekabor-1 powder: Powder 1 62

(b) SEM images of Ekabor-1 powder: Powder 2 62

(c) SEM images of Ekabor-1 powder: Powder 3 63

4.6 Boronized layer thickness of fine microstructure DSS, boronized at

1223 K for 6 hours, using: (a) Powder 1; (b) Powder 2; (c) Powder 3 64

4.7 Relationship between boronized layer and boronizing time with variouspowder particle size 65

4.8 Surface hardness profile of fine microstructure boronized DSS with

different powder particle size 68

4.9 Microhardness of cross-sectioned fine microstructure DSS, boronized

at 1223 K for 8 hours, using Powder 1 boronizing agent 69

4.10 Cross-section hardness profile of boronized fine microstructure DSS as a

function of distance 69

4.11 Relationship between boronized layer thickness and initial pressure at

various surface roughness conditions 71

4.12 Cross-sectional view of specimen boronized at 74 MPa:

(a) 0.9 m Ra, (b) 0.3 m Ra, (c) 0.1 m Ra and (d) 0.03 m Ra 72

4.13 Relationship between surface hardness and initial pressure at various

surface roughness conditions 74

4.14 Optical micrograph showing the hardness indentation variation from theouter layer to the interior of superplastically boronized DSS (boronized at

1223 K for 4 hours and initial pressure of 74 MPa with 00.3 m Ra) 75

4.15 The hardness variation of superplastically boronized DSS as a function of

distance (boronized at 1223 K for 4 hours and initial pressure of 74 MPa

with 00.3 m Ra) 76

4.16 Boronized layer thickness value of boronized as-received DSS and fine

grain DSS at 1223 K for 4 hours 77

4.17 Surface hardness value of boronized as-received DSS and fine grainDSS at 1223 K for 4 hours 77

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4.18 Cross-sectional view of specimen boronized at 1223 K, 4 hours, 74 MPa

and 0.03 m Ra: (a) fine grain DSS; (b) as-received coarse grain DSS 78

4.19 Side view of specimen before and after dual compression method at

compressive strain of 0.4 under 1 x 10-4 s-1 strain rate 80

4.20 Stress and strain relationship at different strain rate 81

4.21 Strain rate sensitivity (m) for dual compression method of superplastic

duplex stainless steel 83

4.22 Cross-sectional view of (a) specimen before compressed; specimens after

compressed at: (b) 1 x 10-2 s-1, (c) 1 x 10-3 s-1, (d) 1 x 10-4 s-1 and

(e) specimen heated for 4000 s without deformation 84

4.23 Microhardness of cross-sectioned superplastic DSS (a) before compressed;

compressed at: (b) 1 x 10-2 s-1, (c) 1 x 10-3 s-1, (d) 1 x 10-4 s-1 and(e) heated for 4000 s without deformation 88

4.24 The hardness variation before and after dual compression method as a

function of distance 89

x