Here this should help
http://www.centuryperformance.com/arp-fastener-material-guide-spg-187.html
Stainless Steel
Ideally suited for many automotive and marine applications because stainless is tolerant of heat and virtually impervious to rust and corrosion. ARP® "Stainless 300" is specially alloyed for extra durability. It's specially polished using a proprietary process to produce a beautiful finish.
8740 Chrome Moly
Until the development of today's modern alloys, chrome moly was popularly considered a high strength material. Now viewed as only moderate strength, 8740 chrome moly is seen as a good tough steel, with adequate fatigue properties for most racing applications, but only if the threads are rolled after the heat treatment. (A standard ARP® practice). Typically, chrome moly is classified as a quench and temper steel that can be heat treated to deliver tensile strengths between 180,000-210,000 psi.
ARP2000
An Exclusive "Hybrid-Alloy" developed to deliver superior strength and better fatigue properties. While 8740 and ARP® 2000 share similar characteristics, ARP® 2000 is capable of achieving clamp loads in the 215,000-220,000 psi range. ARP® 2000 is used widely in short track and drag racing as an upgrade from 8740 chrome moly in both steel and aluminum connecting rods. In this strength level, stress corrosion and hydrogen embrittlement are typically not a problem, provided care is taken during installation.
L19
This is a premium steel that is processed to deliver superior strength and fatigue properties. L19 is a very high strength material compared to 8740 or ARP® 2000, and is capable of delivering clamp loads in the 230,000-260,000 psi range. It is primarily used in short track and drag racing applications where inertia loads exceed the clamping capability of ARP® 2000. Like most high strength, quench and temper steels, L19 requires special care during manufacturing to avoid hydrogen embrittlement. This material is easily contaminated and subject to stress corrosion. It must be kept well oiled and not exposed to moisture.
AERMET 100
With a typical tensile strength of 280,000 psi, Aermet 100 is a new martensitic super-alloy that is stronger and less expensive that the super-alloy austenitic materials that follow. Because Aermet 100 is capable of achieving incredibly high clamping loads, it is ideal for short but extreme environments like Top Fuel, Funny Car, and some short track applications. Although Aermet 100 is a maraging steel that is far superior to the other high strength steels in it's resistance to stress corrosion, it must be kept well oiled and not exposed to moisture.
INCONEL 718
This is a nickel based material that is in the high temperature, super-alloy class, and is found to be equally suitable in lower temperature applications. This material delivers tensile strengths into the 220,000 psi range and exhibits improved fatigue properties. Best of all, Inconel 718 is completely immune to hydrogen embrittlement and corrosion.
ARP® 3.5 (AMS5844)
While similar to Inconel 718, these super-alloys are found in many jet engines and aerospace applications where heat and stress attack the life of critical components. The high cobalt content of this alloy, while expensive delivers a material with superior fatigue characteristics and a tensile strength in the 270,000 psi range. The immunity to hydrogen embrittlement and corrosion of these materials a significant design consideration. These materials are primarily used in connecting rods where extremely high loads, high RPM, and endurance are important factors, such as: Formula 1, Winston Cup, and CART applications.
CUSTOM AGE 625+
This newly formulated super-alloy demonstrates superior fatigue cycle life, tensile strength, and toughness. With complete resistance to atmospheric corrosion and oxidation it sees many uses. ARP® is the first to develop manufacturing and testing processes for fasteners with Custom Age 625+. Best of all, it is less expensive, and expected to soon replace MP-35 as the material of choice in the high strength, super-alloy field. Typical tensile strength is 260,000 psi.
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