Incoloy 803 Introduction

Solid Solution
Strengthened Alloy

Iron

Nickel

Chromium

Corrosion
Resistance

78

Mechanical
Behavior

68

Purity

88

Overview

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INCOLOY® alloy 803 (UNS S35045), an iron-nickel-chromium alloy, is designed for use in petrochemical, chemical and thermal processing applications. The nickel and chromium contents of alloy 803 are higher than those of INCOLOY alloys 800H and 800HT®. The ratios of nickel, iron and chromium are balanced to provide optimum properties in the temperature range of 1550°F (840°C) to 2100°F (1150°C). Alloy 803 is a cost-effective material which provides an exceptional level of high-temperature corrosion resistance in oxidation, sulfidation and carburization environments. INCOLOY alloy 803 exhibits excellent stress-rupture strengths at elevated temperatures. These characteristics, along with a high resistance to carburization and cyclic oxidation, make INCOLOY alloy 803 the material of choice for many severe applications including ID-finned pyrolysis tubing in high-severity ethylene furnaces.

INCOLOY alloy 803 is produced in all major product forms in a wide variety of sizes, finishes and tempers. One unique product form is internally finned, either straight or spiralled fins, cold finished tubing. Strict process controls ensure complete material traceability and structure consistency throughout the manufacture of all INCOLOY alloy 803 products.

Mechanical Properties

INCOLOY alloy 803 has good mechanical strength at room and elevated temperatures. However, like many other iron-nickel-chromium alloys designed for service at high temperatures, INCOLOY alloy 803 can undergo solid state reactions when exposed to intermediate temperatures between 1100°F (590°C) and 1500°F (815°C) for long periods of time. Such reactions can result in the precipitation of phases and compounds which can reduce the ductility and impact strength of alloy components (Table 9). Designers must consider these phenomena when alloy 803 is being used in applications in which it will be exposed to these temperatures for extended periods of time. It may be necessary to solution anneal material that has been so exposed to restore ductility prior to repair or deformation after service.

Corrosion Resistance

INCOLOY alloy 803 is characterized by an impressive resistance to various forms of high-temperature corrosion. Carburization can cause a loss of an alloy’s creep and stress-rupture strength and a reduction in resistance to thermal fatigue. Mixed oxidant carburizing environments are the most typical atmospheres for applications involving heat-resistant alloys. INCOLOY alloy 803 forms a protective oxide in these environments. A more severe atmosphere is created by “oxygen-free” carburizing environments which restrict the formation of protective oxides.

Physical Properties

Mechanical Properties