Influence of Microstructure and Second Phase Precipitation by Adding Al-Ti on the Mechanical Behavior of Austenitic Heat Resistant Steel Castings

Abstract

Heat resistant stainless steel castings are widely used in several industrial sectors working at high temperatures like cement, chemical, heat treatment, metal enameling and other several industries. The purpose of this investigation is to examine the influence of changing microstructures and intermetallic precipitates (Ni3Al, Ni3Ti) by heat treatment on the mechanical properties of heat resistant steel castings of type 11Ni-23Cr-0.35C used at temperatures more than 950 ºC. Aluminum and Titanium were added to the steel melt before tapping the heat into the casting moulds. The change in microstructures after aging heat treatment (850-900 ºC, 85 to 200 h) was detected using scanning as well as optical microscopy. The mechanical properties (high temperature tensile and hardness and creep tests) were measured for all the microstructures obtained in as cast, solution treated and aged conditions. The results showed improved mechanical properties as compared to that for plain heat resistant steel castings, assuring enhancement of life time of treated and aged parts.