Abstract
Five heat resistant steel compositions (Alloy A-E) have been designed based on the Fe-Ni-Cr alloy system in attempts to increase cost performance of conventional heat resistant steels. With systematic additions of C, Si, Co, W, Nb, Mo, and the reduction of Ni content, further strengthening can be provided by formation of various types of carbides such as MC, M7C3, and M23C6. To evaluate their properties, experimental work includes room temperature hardness, 1000°C tensile tests, creep tests under 900°C/65MPa and 982°C/35MPa, and high temperature oxidation of as-cast and pre-oxidized samples at 1000°C, 1100°C and 1150°C. Comparing to the properties commercial HP alloy, the newly designed alloy can exhibit more than 10 times increase in creep rupture life by discontinuous carbide distribution and higher MC to M23C6 ratio caused by Nb, W and Mo addition and Cr decrement. Besides, tensile strength at 1000°C and room temperature hardness is 1.4 times better than that of HP alloy. Furthermore, the oxidation resistance was maintained by pre-oxidized treatment at 1000°C. Advanced heat resistant steels have been developed successfully with much improved cost-performance in this work.