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Synergy Material Technology
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Polycrystalline Cubic Boron Nitride (PCBN)
Polycrystalline cubic boron nitride (PCBN) composites are produced by sintering micron cBN (cubic boron nitride) powders with various ceramic binders yielding hard and thermally stable tool materials. Most PCBN materials have a cemented carbide substrate. CBN is the second hardest material known, after diamond, but has high thermal and chemical resistance. PCBN composites provide extreme resistance to deformation and wear at high temperatures.
About two thirds of all PCBN tools are used for the machining of hardened steels. Other applications are the machining of hard, grey and high-strength cast iron, and cold and hot-work tool steels. The machining of nickel and cobalt-based superalloys is a growing application for PCBN.
Comparison of tool & workpiece hardness
How PCBN works
The effectiveness of PCBN in machining hardened steels is due PCBN’s high hot hardness and chemical stability at elevated temperatures. Self-induced heat generated in the cutting zone reduces the hardness of the material in contact with the cutting tool.
| Property | Al2O3+TiCN (30% Vol) | Tungsten Carbide K10 | PCBN |
|---|---|---|---|
| Vickers Hardness (GPa) | 19 | 17 | 25-40 |
| Fracture Toughness (MPam0.5) | 3.6 | 10.5 | 4.0-7.2 |
| Thermal Conductivity (W/m/°K) | 32 | 100 | 34-100 |
General indicator of applications by cBN content
Standard disc specifications
PCBN with substrate
Outer disc diameter: 75 mm
Useable disc diameter: 70 mm
PCBN layer thickness: 0.7-1.0 mm
Overall thicknesses: 1.6, 2.38, 3.18 and 4.76 mm
(+/- 0.05 mm)
Grades:
cBN (%)
45
50
65
85
90
90
Grain size (µm)
<1
1.5
3
2
4
3
Binder
TiCN
TiC
TiN
AlWCoB
Novel
TiCN-Al
Solid PCBN, conductive
Outer disc diameter: 94 mm
Useable disc diameter: 95% 90 mm
Overall thicknesses: 1.0, 1.6, 2.38, 3.18 and 4.76 mm
(+/- 0.05 mm)
Grades:
cBN (%)
45
50
50
Grain size (µm)
<1
1.5
4
Binder
TiCN
TiC
TiC/TiN
Solid PCBN, non-conductive
Outer disc diameter: 101 mm
Useable disc diameter: 95% 97 mm
Overall thicknesses: 3.18, 4.76 and 6.35 mm
(+/- 0.13 mm)
Grades:
cBN (%)
65
70
90
90
Grain size (µm)
<4
<1
3-10
3-60
Binder
TiC/TiN
TiCN
AlN+AlBx
AlN+AlBx
Tool geometry suggestions
Hardened steel - rough turning
(Left: standard turning; Right: profiling)
Hardened steel - finish turning
(Left to Right: standard turning, thin wall & small internal diameters)
Grey cast iron - through the skin
Grey cast iron - finish machining
Tool manufacture
Suggested edge preparation for hard turning:
Chamfer
standard 20° x 0.2 mm
heavy roughing 20° x 0.2-0.4 mm
Hone
standard 10-20 µm
roughing 20-40 µm
(Left: standard turning; Right: thin wall)
Nose radius
Chamfer
PCBN processing
Tool production, using PCBN, involves several techniques depending upon:
• the tool material and
• the tool application.
The processes involved in tool fabrication are:
