ALLOY 718

NICKEL & SUPER ALLOYS

Home Materials Nickel & Super Alloys Alloy 718

UNS N07718 : ASTM B637 GRADE 630 AMS 5662, 5663 & 5664

GENERAL SCOPE

Alloy 718, a nickel based superalloy, developed initially for use in rotating parts in aerospace and gas turbine applications, has become the preferred material for the manufacture of Wellhead Components, Auxiliary and Down Hole Tools, and Sub-Surface Safety Valves.

The alloy also possesses excellent sub zero toughness and resistance to hydrogen embrittlement, both factors which can be as important as strength and corrosion resistance. Normally supplied using a ‘double vacuum melt’ process – either VIM/VAR (vacuum induction melting, followed by vacuum arc remelting), or VIM/ESR (vacuum induction melting, followed by electro slag refining), though an air melt and double VAR melting practice is also permitted by many material specifications.

Strength levels up to 150 KSI 0.2% PS can be achieved by either careful heat treatment and/or a restricted chemical analysis. 718 is approved for use under NACE MR0175 in a number of different conditions with different hardness restrictions. API 6ACRA includes 718 heat treated to 120ksi and 140ksi strength levels, and it is commonplace for this alloy to be supplied at 125ksi 0.2% yield in compliance with the former.

Howco has significant experience heat treating this alloy to a number of different strength levels, including 125ksi, 140ksi and 150ksi 0.2% yield in line with the relevant standards.

CHEMICAL COMPOSITION

	C	Si	Mn	P	S	Cr	Ni	Mo	Cu	NbCbTa	Ti	Al	B	Fe
Min	.	.	.	.	.	17.00	50.00	2.80	.	4.75	0.65	0.20	.	0.00
Max	0.08	0.35	0.35	0.015	0.015	21.00	55.00	3.30	0.30	5.50	1.15	0.80	0.01	0.00

MECHANICAL PROPERTIES

Condition: Solution Annealed and Age Hardened

U.T.S	150 KSI Min	(1034 N/mm2)
0.2% Proof Stress	120 KSI Min	(827 N/mm2)
Elongation	20 %
Red of Area	25 %
CVN Impacts @ -60°C (-75°F)	40 Joules	(30 ft-lbf)