PCD/CBN Materials

Precision manufacturing requires precision tools. As industries move forward with technology advances and the need for accurate and precise manufacturing processes our customers are asking for precision tools to meet their requirements. Fine, smooth cuts, geometrically perfect threading, grinding and milling applications can be achieved with using the industries top two materials – Polycrystalline Diamond and Cubic Boron Nitride, commonly referred to as PCD and CBN respectively.
Each with their own characteristics, when used in tool making, these materials will provide long lasting, rugged tooling for arduous applications used in making parts for the automotive, aerospace and mining industries and more.

PCD

Created using HPHT process pure carbon is transformed into Polycrystalline Diamond particles – synthetic mini diamonds. These diamonds have been proven to be superior in quality and consistency and have been unchallenged as the toughest material in the world. They possess all the mechanical properties of natural diamonds that are mined throughout the world – hard, strong, stable and tough – but are even better.

Table 1. Mechanical properties of diamond


PCD CBN
Indentation hardness (kg/mm2) 6,000-10,000 4,500
Compressive strength (GPa) 110 43-47
Modulus of elasticity (GPa) 1050 600-800
Thermal conductivity (W/m-°K) 800 150-700
Coefficient of friction 0.05-0.1

 

Using ultra-high pressure(~60 kbar) and high temperature (~1450°C), synthetic diamond particles are sintered together and metallurgically bonded to tungsten carbide substrate. The catalyst to this process is a material called cobalt metal which promotes the intergrowth of the diamond particles under the high temperature and high pressure conditions. The process creates a thin layer of material consisting of a network of diamond to diamond intergranular bonds for a hardened, abrasion resistant cutting surface that remains stable in high temperature applications.

PCD is measured by grain sizes that range from nanometers to hundreds of micrometers, usually referred to as nanocrystalline and microcrystalline. Smaller particles in higher quantity provide higher grade tooling.

Refer to the PCD application guide for the proper PCD tool.

CBN

Cubic Boron Nitride (CBN) is one of the greatest technological advancements for material removal. It was designed specifically for applications involving ferrous materials and is second in hardness to diamond with twice the hardness and four times the abrasion resistance of conventional abrasives. CBN products have exceptional thermal conductivity and exceptional surface integrity.

Cubic boron nitride (CBN) is the second hardest material after synthetic diamond and is created from hexagonal boron nitride under conditions similar to those used to produce synthetic diamond from graphite. The desirable characteristics of an abrasive include high hardness, strength, abrasion resistance, and thermal and chemical resistance, and an ability to maintain sharp cutting edges during use. These characteristics exceed the values of conventional abrasives, such as silicon carbide and aluminum oxide. In particular, the properties of high thermal stability and chemical resistance make it suitable for machining ferrous materials, an area where synthetic diamond abrasives are not norm.

Hardness is a crucial property of any abrasive. However, most abrasives suffer a loss in hardness at the elevated temperatures experienced during application. One of the physical advantages of CBN compared to conventional abrasives is that, in addition to being harder at ambient temperature, it maintains this hardness over a wide temperature range.

CBN abrasives provide higher productivity and dramatically longer tool lives compared to conventional abrasives when grinding, honing and fine finishing hardened ferrous materials and difficult to machine alloys. CBN is firmly established in ‘tool and cutter’ grinding and in mass production grinding operations in the automotive, general engineering and aerospace industries. Application examples include camshafts, crankshafts, fuel injectors, transmission parts, gears, CV joints, power steering pump parts and compressor parts. Some of the many advantages of CBN include improved surface finishes and the production of more favorable compressive residual surface stresses.

ACT