UNS N09706 High Performance Alloys High Mechanical Strength Nickel Iron Chromium Alloy

High performance Alloy 706 (UNS N09706) semi-products for clean energy and power generating

1 PRODUCT

High performance Alloy 706 (UNS N09706) semi-products for clean energy and power generating.

Standard semi-product forms include sheet, strip, plate, round bar, flat bar, forging, hexagon, ring, disc, wire and fastener etc.

2 EQUIVALENT DESIGNATION

GH4706, UNS N09706, INCONEL® ALLOY 706

3 APPLICATION

Alloy 706 is used for a variety of applications that require high strength combined with ease of fabrication. In the aerospace field, the alloy is used for turbine discs, shafts, and cases; diffuser cases; compressor discs and shafts; engine mounts; and fasteners. In addition to aerospace applications, the alloy is used for turbine discs in large industrial gas turbines.

4 OVERVIEW

Alloy 706 is a precipitation-hardenable nickel-iron-chromium alloy that provides high mechanical strength in combination with good fabricability. The characteristics of the alloy are similar to those of Alloy 718 except that alloy 706 is more readily fabricated, particularly by machining.

The substantial nickel and chromium contents provide good resistance to oxidation and corrosion. The primary precipitation-hardening constituents of the alloy are niobium and titanium. The aluminum content also contributes to the hardening response.

The precipitation-hardening system in alloy 706 provides the desirable characteristic of delayed hardening response during exposure to precipitation temperatures. That characteristic gives the alloy excellent resistance to postweld strain-age cracking.

5 CHEMICAL COMPOSITION (wt%):

Table 1 (wt%)

6 PHYSICAL PROPERTIES

Density (Annealed):ρ=8.04 g/cm³ (0.291 lb/in³)

Density (Precipitation hardened):ρ=8.08 g/cm³ (0.292 lb/in³)

Melting temperature:1334-1371℃ (2434-2499°F)

Specific heat at 70°F (21°C): 0.106 Btu/lb•°F (444 J/kg•°C)

Permeability at 200 oersted (15.9kA/m)

Annealed

74°F (23°C) 1.011

-109°F (-78°C) 1.020

-320°F (-196°C) Magnetic

Precipitation-Hardened

74°F (23°C) 1.010

-109°F (-78°C) 1.040

-320°F (-196°C) Magnetic

7 METALLOGRAPHY

Alloy 706 is a precipitation-hardenable alloy with a face-centered-cubic crystal structure. The alloy is strengthened by the precipitation of a gamma prime or gamma double-prime phase during heat treatment in the 1100-1400°F (595-760°C) temperature range. Heat Treatment A produces both the gamma prime, which has a face-centered-cubic structure, and the gamma double prime, which has a body-centered-tetragonal structure. Heat Treatment B normally produces only the gamma prime phase. The phases have a Ni3 (Nb, Ti, Al) composition. They are not visible at magnifications achieved by optical microscopy; electron microscopy is required for resolution. Overaging or extended service at precipitation-hardening temperatures results in a transformation of the phases to a needle-shaped, orthorhombic Ni3Nb structure. That structure may be visible with optical microscopy.

8 MECHANICAL PROPERTIES

The high-strength of precipitation-hardened alloy 706 is maintained at temperatures up to 1300°F (705°C). Optimum mechanical properties for the intended service temperature are achieved by the use of one of two heat treatments.

Typical Room Temperature Tensile Properties of Hot Finished Material

9 CORROSION RESISTANCE

The composition of alloy 706 enables it to resist corrosion in various environments. The alloy’s chromium content provides resistance to oxidizing media, and its nickel content provides resistance to reducing environments. Table 7-1 lists corrosion rates for the alloy in several acid solutions at boiling temperatures. Other tests have shown the alloy to have poor resistance to boiling 50% sulfuric acid and to boiling 38% and concentrated hydrochloric acid.

The nickel content of alloy 706 gives it resistance to both chloride-ion and hydroxyl-ion stress-corrosion cracking. Stressed specimens did not crack in 30 days of exposure to boiling 42% magnesium chloride. A test in boiling 50% sodium hydroxide resulted in a cracking time of 5 days.

Table 9-1 Corrosion Rates in Boiling Acid Solutions

a Mils penetration per year.

10 MICROSTRUCTURE

Alloy 706 is a precipitation-hardenable alloy with a face-centered-cubic crystal structure. The alloy is strengthened by the precipitation of a gamma prime or gamma double-prime phase during heat treatment in the 1100-1400°F (595-760°C) temperature range. Heat Treatment A produces both the gamma prime, which has a face-centered-cubic structure, and the gamma double prime, which has a body-centered-tetragonal structure. Heat Treatment B normally produces only the gamma prime phase. The phases have a Ni3 (Nb, Ti, Al) composition. They are not visible at magnifications achieved by optical microscopy; electron microscopy is required for resolution. Overaging or extended service at precipitation-hardening temperatures results in a transformation of the phases to a needle-shaped, orthorhombic Ni3Nb structure. That structure may be visible with optical microscopy.

11 WORKING INSTRUCTION

Alloy 706 has good working characteristics and is readily fabricated by conventional procedures for high- strength alloys. Of particular significance are the machinability and weldability of the alloy.

Hot forming

Alloy 706 has excellent hot formability at temperatures from 1600°F (870°C) to 2100°F (1150°C). Test results indicate, however, that optimum mechanical properties are obtained with hot-working temperatures in the 1800°F (980°C) to 2100°F (1150°C) range.

Cold forming

Cold forming of alloy 706 is performed by standard methods for high-nickel alloys. The work-hardening rate of the alloy is shown in Figure 1. The cold-forming characteristics of alloy 706 are similar to those of alloy 718. Alloy 706, however, is somewhat softer in the annealed condition and requires lower forces for deformation.

Figure 1 Effect of cold work on hardness of alloy 706 and other materials.

Machining

Good machinability is one of the outstanding characteristics of alloy 706. The superiority of alloy 706 over some other high-strength alloys is shown by the tool- life/cutting-velocity comparison in Figure 2.

Figure 2 Machinability of annealed material. Specimens were machined with carbide tools and with water-soluble oil as coolant.

12 STANDARD SPECIFICATION

Rod, Bar, Wire, Forgings, and Forging

SAE AMS 5701

SAE AMS 5702

SAE AMS 5703 Bars, Forgings and Rings

Plate, Sheet, and Strip

SAE AMS 5605

SAE AMS 5606 Sheet, Strip and Plate

13 COMPETITIVE ADVANTAGE:

(1) More than 50 years experience of research and develop in high temperature alloy, corrosion resistance alloy, precision alloy, refractory alloy, rare metal and precious metal material and products.
(2) 6 state key laboratories and calibration center.
(3) Patented technologies.

(4) Ultra-purity smelting process: VIM + IG-ESR + VAR

(5) Excellent high performance.

14 BUSINESS TERM