Application of 0Cr17Ni4Cu4Nb(17–4PH)

Introduction

Type 17-4 PH steel is a steel alloy composed of chromium, nickel, copper, and niobium, with the abbreviation of 17Cr-4Ni-4Cu-Nb (17-4 PH). It is one of the most widely used high-strength stainless steel alloys, having excellent resistance to molten metals and solutions as well as to oxidation at high temperatures. Because of its ability to be formed and welded yet still maintain superior strength, 17-4 PH steel is used for a variety of applications in the aerospace and industrial markets. This paper will discuss the chemical composition of type 17-4 PH steel, the effects of heat treatment, and its various industrial and aerospace applications.

Chemical Composition

17-4 PH alloy steel is composed primarily of chromium, nickel, and copper, with minor amounts of molybdenum and niobium. The standard composition by weight is 17% chromium, 4% nickel, 4% copper, and 0.2% niobium. The chemical composition of type 17-4 PH steel provides excellent hardness and strength with moderate corrosion resistance.

Heat Treatment

Type 17-4 PH steel is commonly heat treated to increase its strength and toughness. The steel is first heated slowly to temperatures between 930°F to 1040°F and then held at this temperature to relieve any stresses. The material is then cooled in air before going through a final heat treatment with a higher temperature of between 1450°F and 1550°F.

Industrial Applications

Type 17-4 PH steel is widely used in industrial applications due to its high strength and corrosion resistance. The steel is often used in components with high mechanical stress, such as blades and turbine discs, shafts, gears, and bearings. It is also used in aerospace and chemical processing components.

Aerospace Applications

Type 17-4 PH steel is widely used in aerospace applications due to its strength and corrosion resistance. It is used in components like landing gears, turbine discs, landing strut housings, shafts and bearings, and thrust washers. It is also used in fasteners, fuel nozzle brackets, and electrical connectors.

Conclusion

Type 17-4 PH is a high-strength stainless steel furnace alloy that is composed primarily of chromium, nickel, copper, and niobium. It has excellent mechanical properties, including high hardness and strength, and moderate resistance to corrosion. 17-4 PH is widely used for a variety of industrial and aerospace applications, such as turbine discs, shafts, gears, and landing gears. Its high strength and corrosion resistance make it an excellent choice for these types of applications.

Inconel 718 (UNS N07718) is a precipitation hardened nickel-base alloy designed for use from cryogenic to elevated temperatures, up to around 1300°F (704°C). The alloy presents some significant characteristics, such as:

• High strength, both in room temperature and elevated temperatures

• High oxidation resistance up to 1800°F (982°C)

• Good corrosion resistance

• Stress corrosion crack resistance

• Low vs volatile performance

• Low magnetic permeability

• High rate of thermal conductivity

Therefore, Inconel 718 is typically used in applications such as aerospace industry, land-based turbine engines, nuclear reactors and marine industry, where fatigue resistance and creep rupture are important factors.

Inconel 718 is available in several form, the most common ones being: rod and bar products, sheet and plate material, seamless and welded pipe, fittings and flanges, structural products, forgings and fasteners.

Because of its high strength, Inconel 718 is also used for cryogenic applications. Some of its most common applications include valve and gate components, fasteners, compressor components and shafts, springs and aerospace components, as well as pressurizing and fuel injection systems.

The alloy generally contains 17.0-21.0 % of chromium, 4.0-7.0 % of nickel, up to 0.35 % of carbon, 0.80-1.8 % of molybdenum, and 0.20-0.8 % of titanium, together with trace amounts of other elements among them manganese, silicon and sulfur. Inconel 718 is available in annealed condition for machining operations and also in age-hardened condition for products that require higher strength and durability.