Material Innovations
April 2002
No-flake thin-film coating
 Casidiam on wrist pins allows for an increase in engine cylinder pressure. |
The use of its Casidiam (generic name: diamond-like carbon) thin-film coating has nearly eliminated wrist pins as a source of engine failure for NASCAR engine builders since it was introduced into the racing series in 1999, according to Anatech Ltd.
At that point, demands related to high power, high rpm, oil-pan vacuum, and low-viscosity lube oil put wrist pins made of traditional alloys at about their limits of capability. Casidiam on wrist pins allows for an increase in cylinder pressure that translates into higher power. For that reason, engine makers for other racing series also are now using Casidiam as well.
Anatech says Casidiam is the first coating that offers the properties of both great hardness and low friction, making it beneficial not only for wrist pins made of steel, but also for those made of titanium.
Casidiam is applied via chemical vapor deposition. Parts are placed in a processing unit, then a vacuum is drawn and electrical energy applied. The ionized gaseous environment in the unit changes carbon from vapor to solid form, causing it to condense on the surface of the parts. Some of the carbon forms diamond, or tetrahedral, bonds, and the rest of the coating is hard carbon in tightly bonded graphitic form.
Casidiam is applied by Anatech in a thickness ranging from 0.002-0.004 mm (0.00008-0.00016 in)—0.002 mm (0.00008 in) is used for race engine parts. "When we started serving the racing industry, we didn't know what impact that might have on part manufacturing dimensions," said engineer John Roderique, Manager of Sales and Marketing for Anatech. "The first engine builders who tried Casidiam found that it solved wear problems without having to change part dimensions." No post-processing steps are required.
Casidiam also has found a niche in extending the life of titanium intake valves. The coating has proven to be effective with several valve-seat materials, including nodular iron, silicon aluminum bronze, 6055 bronze, and several copper beryllium alloys.
Connecting rods are another successful Casidiam application. In 2001, Arrow Racing Components replaced moly on the big end shoulders of several titanium connecting rods for 8.0-L Pro Stock drag-racing engines. Under high flexure due to detonation or other causes, moly has been known to flake off the shoulder area, leaving the engine builder uncomfortable with the rod's ability to resist galling. In cases such as this, moly must be stripped, then reapplied. Casidiam, on the other hand, is flexible and does not delaminate. Proof of that, Anatech notes, is the fact that Casidiam-coated rods lasted the entire 2001 season for several prominent racing teams.
Some NASCAR teams have decided that for the 2002 season they would trade some mass from wrist pins to other engine components, making the pins more flexible. Roderique said the teams were not concerned about relying on Casidiam to prevent galling when pin flexure squeezes the oil film away from the piston-pin clearance.
Valves and valve locks are two other applications Anatech is introducing to NASCAR engine builders for 2002.
A microhardness tester from Fischer Technology, Inc. is used for inspection. For thin coatings, the measuring tool should not indent more than a tenth of the coating's depth to isolate the coating properties from the substrate properties, and the Fischerscope has that capability, noted Roderique.
- Patrick Ponticel
The steely side of metal
 ULSAB-AVC virtual study concepts reflect a SAFE (Safe, Affordable, Fuel Efficient, Environmentally Responsible) motif. |
A four-door gasoline-powered sedan that meets 2004 U.S. and European crash safety requirements with five-star performance, carries a $9500 estimated manufacturing cost, and achieves a city/highway average of 52 mpg is made of what?
The answer, according to presentations at the SAE Congress in March by members of the American Iron and Steel Institute (AISI) is Advanced High-Strength Steels (AHSS). "These new, high-tech steels are an entirely new category of materials that combine very high-strength with excellent formability," said Andrew Sharkey, President and CEO of the AISI, based in Southfield, MI.
Extensive use of AHSS defines the Ultra Light Steel Auto Body-Advanced Vehicle Concept (ULSAB-AVC) project. "ULSAB-AVC is the latest in a continuing series of customer-centered initiatives our industry has executed over the past decade," said Sharkey, noting that various studies—ranging from a fabricated body-in-white (the ULSAB project of 1998) to the development of lightweight trucks for both military and commercial use (the IMPACT project)—demonstrate the viability of lightweight steel. So far, more than $44 million has been invested in the studies.
The ULSAB-AVCs, virtual vehicles dressed as both a 998-kg (2200-lb) gasoline-powered car and a 1031-kg (2273-lb) diesel-powered car, are represented via a two-door European C-Class hatchback and a four-door North American midsize sedan. AVCs reflect the latest advancements with High-Strength Steels (HSS) and AHSS.
The original ULSAB used mainly mild and conventional HSSs with yield strengths up to 50.8 ksi (350 Mpa). The ULSAB-AVC used steel with yield strengths no lower than that figure, according to Blake Zuidema, Director, Center for Product and Applications Development for National Steel Corp.
Body structure of the ULSAB-AVC is comprised of approximately 80% AHSS with the remaining 20% represented in other grades of HSS. The body structure contains 81 major parts and has a mass of 218 kg (481 lb).
 Stamping dominates the manufacturing processes for ULSAB-AVC. Click to enlarge |
AHSS grades incorporate multi-phase microstructures, which contain martensite, bainite, and/or retained austenite. The resulting high-performance strength and formability "is an advantage for automotive applications," said Jody Shaw, Manager, Technical Marketing for U.S. Steel Corp.
The cyberspace concept vehicles use advanced steels in areas beyond the body structure. For example, the double wishbone front suspension uses AHSS tailored blanks. The instrument panel beam, fuel tank, seat frames, bumper beams, wheels, and closures (hood, doors, deck lid) are steel. The closures incorporate HSSs and AHSSs as well as tailor welded blanks and tubular hydroformed components.
"Tailored blanks account for nearly 40% of the body structures, with hydroformed parts making up more than 20% and tailored tubes comprising 6%. Stamping is the predominant steel forming method in ULSAB-AVC with more than 70% of the body structures and closure parts warranting use of this process," said Marcel van Schaik, Director of Materials Technologies for AISI.
Computer simulation tests predict the AVCs would earn five-star safety ratings in the U.S. and Europe for full-frontal, frontal-offset, side-impact, and side-pole crashes (the safety ratings would tie to the anticipated requirements for 2004). "We didn't feel that it was appropriate to build (a hardware prototype) now to prove what's already validated in our models," said Ron Krupitzer, Senior Director-Automotive Applications for AISI.
The ULSAB-AVC study involved 33 steel producers. Porsche Engineering Services, Inc. was contracted for design and engineering management.
- Kami Buchholz
