High Strength Steel with Corrosion Resistance and High Toughness

[Astronuc]

I periodically browse the literature for new products. In the August 2006 issue of Advanced Materials & Process (from ASM International), I found an article on a new high strength steel from Carpenter Technology Corp. (Cartech)

Cartech Custom 465 (find it at www.cartech.com)

Custom 465 stainless steel is a premium double vacuum-melted, martensitic, age-hardenable alloy that offers a unique combination of high strength, toughness, and corrosion resistance. It is capable of ultimate tensile strength in excess of 250 ksi (1722 MPa) when aged at 950°F (H950 condition). This strength is higher than that of any other historically available precipitation-hardenable stainless steel long product. Aging temperatures ranging from 950 to 1050°F can be selected to achieve the balance of strength, toughness, and resistance to stress-corrosion cracking needed for specific applications.

The H950 condition is the most common treatment for achieving higher strength together with good toughness and excellent notch tensile strength. The H1000 condition may be chosen for higher toughness at a slightly lower strength level. This condition provides a superior combination of strength, toughness, fabricability, and resistance to stress-corrosion cracking.

Custom 465 is an alternative to 17-4 PH steel, with more than twice the impact resistance as 17-4 PH

Composition (w/o)

Cr: 11-12.5
Ni: 10.8-11.3
Mo: 0.8-1.2
Ti: 1.5-1.8
Fe: bal

See US Patents: 5681528, 5855844

- Marine engine shafts

Howard Arneson is known for groundbreaking marine racing designs such as the famous Arneson surface drive propulsion system. He knew he was pushing material limits when he harnessed a 4500-hp Lycoming gas turbine, like those in U.S. Army helicopters, to just one propeller shaft in his newest catamaran racing boat. This is three times the power load that is normally applied to a marine propulsion shaft.

Zeiger Industries of Canton, Ohio, was asked to fabricate the propeller shaft from 17Cr-4Ni PH stainless steel. The finished shaft measured 40 inches long by 2.5 inches in the center, tapering down to 1-7/8 inch at both ends. After careful installation of the shaft, the powerful racer was taken for a test cruise on the Pacific Ocean. Following 50 hours of running time at speeds around 100 mph, the shaft broke off, dropping to the bottom of the sea with its propeller.

A new shaft made from Custom 465 was produced and placed into the catamaran. The engine was tested under exceedingly severe loading conditions. The initial test involved accelerating the catamaran to 100 mph in just 12 seconds, which was accomplished successfully. The catamaran was then accelerated to 175 mph, and held for several hours at that speed. For approximately four months, the catamaran was cruised at sustained high speeds, 50 to 100 miles at a time, several times a week, without any trace of a problem.

After this extended period of intense service, the propeller was removed and no marks or signs of wear were found even where the propeller engages the spline. This serves to illustrate the advantages of 465 over other PH stainless alloys, as it matches them in resistance to stress corrosion cracking while providing markedly higher strength.

 

[Gokul43201]

Custom 465 stainless steel is a premium double vacuum-melted, martensitic, age-hardenable alloy that offers a unique combination of high strength, toughness, and corrosion resistance. It is capable of ultimate tensile strength in excess of 250 ksi (1722 MPa) when aged at 950°F (H950 condition).

Holy cow - 250 ksi in a stainless? That's like a maraging steel! Amazing!

 

[PerennialII]

... got to get some of that and try how it breaks & fails.

 

[FredGarvin]

I've used a fair amount of the custom alloys, especially 450. 465 has been around a bit. MMPDS has it listed in it's references, but the predescessor, MIL-HDBK-5H didn't.

I really wonder what they were thinking of when making a highly loaded shaft out of 17-4. That is not the best pick, especially with splines. My first selection would have been Inco 718.

 

[Astronuc]

Holy cow - 250 ksi in a stainless? That's like a maraging steel! Amazing!

Composition and thermo-mechanical processing.

I don't know how well 718 would have held up in seawater.

I was wondering wondering how well AL-6XN® alloy (UNS N08367) would do. This is a specialty steel by Allegheny Ludlum for marine applications like landing gear on naval aircraft.

 

[FredGarvin]

A lot of our shafts are 718 and they have to survive operating is salty environments. However they get the advantage of not having been completely immersed constantly over a period of time. I think I'll have to look into that part.

 

[aslats]

I periodically browse the literature for new products. In the August 2006 issue of Advanced Materials & Process (from ASM International), I found an article on a new high strength steel from Carpenter Technology Corp. (Cartech)

Cartech Custom 465 (find it at www.cartech.com)



Custom 465 is an alternative to 17-4 PH steel, with more than twice the impact resistance as 17-4 PH

Composition (w/o)

Cr: 11-12.5
Ni: 10.8-11.3
Mo: 0.8-1.2
Ti: 1.5-1.8
Fe: bal

See US Patents: 5681528, 5855844

- Marine engine shafts

I wonder how the fabrication characteristics of 465 compare to 17-4 , in terms of shrinkage and warping during heat treat?

 

[Astronuc]

I wonder how the fabrication characteristics of 465 compare to 17-4 , in terms of shrinkage and warping during heat treat?

See the Custom 465 datasheet and look for 'Average Size Change (Contraction)' under Heat Treatment
http://www.cartech.com/techcenter.aspx?id=1692&searchtext=Custom%20465