Demand for better performance, efficiency and accuracy in
manufacturing is driving continuous improvement in the
Mineral-based abrasives are used for grinding and smoothing
applications, and have been an industrial tool for centuries,
with metalworking generally topping the list of key
Conventional mineral abrasives include silicon carbide,
aluminium oxide, silica, garnet and quartz – minerals
which occur naturally in the earth’s crust.
But with the evolution of the way metals are used, and now
that they are being replaced with lighter, stronger, more
flexible materials in everything from cars to industrial
machinery, new approaches are starting to emerge to optimize
the ways in which component parts are shaped and sharpened.
The automotive sector is one of the fastest-growing
application areas for abrasives.
"If you look at the number of cars being produced –
in the United States, but also globally – over the
past few years, the numbers have been pretty robust," Jeff
Wherry, managing director of the country’s Unified
Abrasives Manufacturers’ Association (UAMA), told
In fact, US vehicle production fell by around 8%
year-on-year in 2017 to 11.2 million units, according to
statistics published by the International Organization of Motor
Vehicle Manufacturers (OICA). Of this total, just over 3
million were passenger cars and 8.15 million were commercial
Globally, however, vehicle production grew by around 2.4%
last year, to 97.3 million units (73.5 million passenger cars
and 23.9 million commercial vehicles), OICA data showed. This
was driven by output increases in China, France, Japan and
Turkey, among others.
"Abrasives are used in almost every part of manufacturing
cars, including in the electronics and seating, so when car
production performs strongly, abrasives demand responds
accordingly," Wherry said.
The trend toward lighter weight components to improve fuel
efficiency has meant that plastics and composites are beginning
to be used more widely in the automotive market as alternatives
to metal parts, according to Wherry.
This trend has been widely regarded as a threat to abrasives
demand, because the kinds of tough, mineral-based materials
that are used for metalworking are not needed to finish plastic
But Wherry believes that this threat is exaggerated. "What
replacements [in the automotive sector] that need to be made
with plastics have already been accomplished," he said. "The
abrasives manufacturers I speak to say that business has never
been so good."
The global abrasives market was 11.8 million tons (10.7
million tonnes) in 2016, according to analysis by US-based
market research consultancy Grand View Research (GVR).
In terms of volume, GVR has forecast that the market will
expand at a compound annual growth rate (CAGR) of 4.5% until
2025, when it will be worth $59.3 billion.
The metal fabrication sector is expected to be the fastest
growing market for abrasives, with a CAGR of 5.2%, driven by
the automotive and aerospace industries.
|Polycrystalline cubic boron nitride (PCBN) is a
superabrasive used for machining
Harder, better, faster, stronger
One of the chief goals for automotive manufacturers is to
reduce their production costs, to bolster margins and help them
to remain competitive in an increasingly crowded market.
Abrasive grinding wheels are necessary tools in the cutting
and finishing of parts for cars, which are made from steel,
aluminium and other durable materials, such as carbon
These parts are often overlaid with wear-resistant coatings,
including ceramic coatings. These enhance their resistance to
corrosion, but make them more difficult to shape and finish
during the manufacturing process. Consequently, grinding wheels
can quickly wear out and have to be replaced frequently.
One attempt to reduce the replacement rate has been the
development of so-called "superabrasives" – extremely
durable materials made from industrial minerals and metals
treated at extremely high temperatures.
Conventional abrasives are typically natural grains that are
fused or blended with other abrasive grains to make a grinding
wheel with the right characteristics for the intended
The hardness of these conventional grains is usually in the
range of 2,100-2,500 on the Knoop scale, a micro-hardness test
developed by the US’ National Bureau of Standards
(now NIST) in 1939.
The hardest known superabrasives are made from synthetic
diamonds, which have a Knoop hardness around 7,000 and are made
Cubic boron nitride (CBN) is the second-hardest material
known after synthetic diamond. It has a Knoop hardness of
4,700, and is synthesized from hexagonal boron nitride under
conditions similar to those used to produce synthetic diamond
The process which raw materials undergo to produce
superabrasives is known as vitrification. The word comes from
the Latin vitreum, meaning "glass", and it refers to
the transformation of a substance into a glass- or ceramic-like
material – technically, a non-crystalline amorphous
This is usually achieved by heating materials until they
liquidize before cooling them rapidly, so that there is no time
for crystals to form. This results in a vitrified solid.
Vitrified diamond and vitrified CBN grinding wheels are
regarded as being among the most efficient grinding
superabrasive products available.
Diamond abrasives are typically used for non-metallic and
non-ferrous materials, while CBN is mostly used to grind
metals. Diamond abrasives are not usually suitable for grinding
steel because the carbon in the diamond reacts with the carbon
content of the steel, wearing down the abrasive tool too
More and more manufacturers are looking into the use of
superabrasives to optimize their grinding processes, according
to David Goetz, corporate applications engineer at Norton
Abrasives, a subsidiary of French industrial conglomerate
Saint-Gobain, based in Ontario, Canada.
Superabrasives are considerably more expensive than
conventional abrasives, but the payback in performance and
longevity is greater, so manufacturers will use them if the
value of the end-product is high enough to justify the input
Superabrasives are more thermally stable and durable than
conventional abrasives, so they give a longer life for grinding
wheels, particularly in demanding applications. They also
typically offer a much higher G-ratio (the ratio of the volume
of material ground to the volume of wheel wear) than other
The G-ratios of conventional abrasives are usually in the
1-20 range, ceramics in the 10-200 range, while superabrasives
are in the 500-10,000+ range, depending on the application.
Because higher G-ratios typically equate to shorter grind
cycles and more jobs per hour, grinding with superabrasives can
increase productivity. Superabrasives do, however, require
higher machine stiffness compared with conventional abrasives,
because they are less forgiving.
|Synthetic diamonds are made from heating graphite to
high temperatures to form the hardest material
Instytut Fizyki Uniwersytet Kazimierza Wielkiego, via
Diamonds grind forever
One of the companies spearheading the development of diamond
superabrasives is Element Six, a private company which is part
of the De Beers diamond business empire.
Founded in 1946 and with its headquarters in Luxembourg, the
company sells super-hard engineering tools all over the world,
with manufacturing sites in Ireland, Germany, South Africa and
In 2013, and at a cost of £20 million ($25.9 million),
Element Six opened the world’s largest and most
sophisticated research and development facility for synthetic
diamond supermaterials at the Harwell Campus in Oxford, UK. The
unit employs more than 100 expert scientists, engineers and
"Synthetic diamonds are harder than traditional abrasive
materials," Hubert Koegel, global sales director for automotive
and aerospace at Element Six, told Industrial Minerals.
The extreme properties of synthetic diamonds, including the
highest known thermal conductivity and electromagnetic
transmission, make them ideal for a variety of advanced
industrial applications, such as mining and tunneling, road
planing (stripping off a road surface before replacing it), and
various uses in the automotive industry, he added.
Element Six makes a range of abrasives for the automotive
sector, including diamond and CBN powders for grinding and
finishing metal surfaces and glass; polycrystalline diamond
(PCD) materials for cutting aluminium or carbon
fiber-reinforced polymers (CFRP); polycrystalline cubic boron
nitride (PCBN) used in finish machining for steel in drivetrain
gears and shafts; and tungsten carbide burr blanks used for
metal cutting and the removal of rough edges.
"Automotive customers require faster, more precise
machining, with materials that enable a longer tool life and
reliable wear," Koegel said.
"The automotive market is very significant for Element Six,
and we expect it to remain that way due to the emergence of new
technologies, such as hybrid and electric cars, as well as
changes in trends of mobility," he added. "Urbanization and the
increasing mobility craved by individuals around the world will
create new opportunities for everyone in the automotive
|American and, increasingly, European drivers are
choosing SUVs and trucks over
smaller car models, pushing up the demand for
Mic, via Flickr
Changing market demands
The shift from conventional abrasives to vitrified CBN
technology in grinding automotive components has been driven
mainly by the machine-tool builders which serve the vehicle
Machine tool builders have had to innovate to meet the
demands of automotive producers for higher productivity, and
have worked with abrasives manufacturers to develop new
vitrified CBN products.
The new developments lower the cost per unit of automotive
parts by making longer-lasting, faster-grinding abrasives with
higher material removal rates.
Advances in vitrified bond technology, coupled with more
choice in superabrasive grain types, mean that abrasive wheels
can perform for longer at the same power level, or lower power,
than traditional grinding wheels.
"This is a key benefit, because new advanced materials such
as High-Velocity Oxygen Fuel ([HVOF] coatings are being
introduced for today’s gas engine components,"
Norton’s Goetz said.
He explained that one of Norton’s principal
objectives was to reduce the number of machining steps between
the "blank" material and the final product.
Abrasives that stay sharper for longer and have a much lower
energy-to-grind ratio also help to reduce the stress and heat
introduced to an automotive part during the manufacturing
process, which improves the structural integrity and safety of
the finished vehicle.
New developments in superabrasives
Although vitrified CBN is still the most common
superabrasive technology used today, there has been a trend
toward using more plated and metal single layer (MSL) products
– such as nickel-bond grinding wheels.
Superabrasive product selection is process-driven. The
geometry of the part being worked, stock removal and finish
requirements, as well as the material being ground, all help to
determine the grain size and type, the grade, concentration and
bond. Their matrices of performance benefits are used by
manufacturers to justify to customers why they should shift to
super or metallic abrasives from conventional abrasives.
So far, the shift to superabrasives has not generally been
regarded as having a negative effect on prices for conventional
abrasive minerals, where bulk pricing has been fairly steady
for some time.
Strong demand for conventional abrasives minerals in the
steelmaking industry has generally supported prices, while
Chinese supply has been brought under control after a few years
of undisciplined production and export.
UAMA’s Wherry said that although there is a
definite trend toward the use of synthetic and superabrasives,
the market for natural and conventional abrasives will remain
strong, at least in the US.
The US abrasives sector is benefiting from the repatriation
of the industry from Asian competitors, he added.
"There was a time when people were very keen to take
advantage of China’s low-cost labor and lax
environmental standards for producing abrasives products there
and importing them into the US," he said. "But recently there
has been some concern about the quality of Chinese material,
and manufacturers have complained, so some companies are
beginning to rethink their strategies."
This shift is backed up by anecdotal evidence from other
sectors, such as aluminium, but is taking some time to
materialize in abrasives.
According to the US Geological Survey (USGS), US abrasive
mineral production in the first quarter of this year was flat
compared with January-March 2017.
Imports of crude fused aluminium oxide totaled 35,400 tonnes
during the period, 51% more than in the first quarter of 2017.
Of this year’s first-quarter imports, 22,100
tonnes, or 64%, came from China, up from 14,500 tonnes (62%) in
For silicon carbide, all but 100 tonnes of the
US’ 11,600 tonnes of imports came from China in
the first quarter of last year. In the equivalent period this
year, the US imported 26,700 tonnes of silicon carbide, 22,000
tonnes, or 82%, of which was from China.
Wherry felt strongly that change was under way and believed
that the election of Republican Donald Trump as US president in
2016 "was the best news the US economy has seen in 30
"Trump’s election was very good news for US
abrasives manufacturers, certainly," Wherry said. "His focus
has been on creating a level playing field in terms of tariffs,
so US companies have a chance to compete fairly with