Abstract
It is a well known fact that all high temperature materials and alloys have certain limitations and the optimum choice is often a compromise between various factors such as the mechanical constraints and compatibility at maximum temperature of operation, environmental constraints as imposed by the process conditions of high temperature, ease of fabricability and repair, cost-effectiveness and availability. Alloys designed to resist high temperature corrosion have existed since the beginning of the 20lh century. Carbon steel, a workhorse of many industries, loses its usefulness above 538°C (1000°F) both due to strength degradation and corrosion. Alloy steels with chromium and molybdenum additions have expanded the useful temperature range for high temperature applications. However, with the increasing severity of high temperature environments encountered in modern day industries, there has been a need for an alloy which can provide a combination of properties of both good mechanical strength as well as high temperature corrosion resistance to various modes of degradation (oxidation, carburization, metal dusting, etc.) up to 1200°C.
This paper describes the development of one such nickel base alloy – alloy 602CA (UNS N06025) which has provided an unique combination of properties by optimization of various alloying elements. Since its introduction to the market in the early 1990’s, this alloy has found numerous applications in the heat treat industry, annealing furnaces, furnace rolls, furnace belts, direct reduction of iron-ore technology to produce sponge-iron, calciners to produce very high purity alumina, calciners for chrome-iron ore for producing ferro-chrome, calciners to reclaim spent nickel catalysts, catalytic converters, exhaust flaps and glow plugs in the automotive industry, refineries, petrochemical industries, nuclear waste vitrification processes and many others.. A brief description of some of these applications is also presented in this paper.
