Super Alloy Nicrofer 7016 TiAl (UNS N07751)

Topics Covered

Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Fabrication and Heat Treatment
     Machinability
     Forming
     Welding
     Heat Treatment
     Forging
     Hot Working
     Cold Working
     Annealing
Other Designations
Applications

Introduction

Nicrofer 7016 TiAl alloy is a precipitation hardenable nickel-chromium-iron alloy that exhibits good corrosion resistance at high and low temperatures. The alloy also has excellent mechanical properties in cryogenic environments. The alloy is very similar to nicrofer 7016 TiNb alloy, except that its slightly modified composition imparts improved stress-rupture properties at 870°C (1600°F).

The following section will provide an overview of nicrofer 7016 TiAl alloy.

Chemical Composition

The chemical composition of nicrofer 7016 TiAl alloy is outlined in the following table.

Element Content (%)
Chromium, Cr 14 - 17
Iron, Fe 5-9
Titanium, Ti 2-2.6
Manganese, Mn 1
Aluminum, Al 0.9-1.5
Niobium+Tantalum, Nb+Ta 0.7-1.2
Silicon, Si 0.5
Carbon, C 0.1
Sulfur, S 0.01
Nickel Balance

Physical Properties

The following table shows the physical properties of nicrofer 7016 TiAl alloy.

Properties Metric Imperial
Density 8.2 g/cm3 0.296 lb/in3
Melting point 1390-1430°C 2540-2600°F

Mechanical Properties

The mechanical properties of nicrofer 7016 TiAl alloy are displayed in the following table.

Properties Metric Imperial
Tensile strength (Solution treated) 782 MPa 113 ksi
Yield strength (Solution treated) 391 MPa 57 ksi
Elongation at break (Solution treated) 42% 42%

Thermal Properties

The thermal properties of nicrofer 7016 TiAl alloy are given in the following table.

Properties Metric Imperial
Thermal expansion co-efficient (@100°C/212°F) 13.2 µm/m°C 7.3 µin/in°F
Thermal conductivity (@20°C/68°F) 10.5 W/mK 73 BTU.in/hrft².°F

Fabrication and Heat Treatment

Machinability

Conventional machining techniques that are used for machining iron-based alloys can be used.

Forming

Nicrofer 7016 TiAl alloy has excellent ductility, and can be readily formed by all conventional techniques.

Welding

The alloy can be welded using commonly used welding techniques such as gas-tungsten arc welding, shielded metal-arc welding, gas metal-arc welding and submerged-arc welding.

Heat Treatment

Nicrofer 7016 TiAl alloy is heat treated at 1177°C (2150°F) for atleast 1 h and air cooled.

Forging

The alloy can be forged at the temperatures ranging from 1038 to 1204°C (1900 to 2200°F).

Hot Working

Hot working of nicrofer 7016 TiAl alloy can be accomplished in the temperature range of 982 to 1204°C (1800 to 2200°F).

Cold Working

Cold working may be performed using standard tooling.

Annealing

The alloy is annealed at 1177°C (2150°F) followed by air cooling.

Other Designations

An equivalent designation to nicrofer 7016 TiAl alloy includes DIN 2.4694.

Applications

Nicrofer 7016 TiAl alloy finds application in exhaust valves on heavy duty diesel engines.

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