Influence of Sintering Conditions on Microstructure and Mechanical Properties of Alloy 218 Steels by Powder Metallurgy Route

In this work, Alloy 218 (UNS S21800) type steels are made through powder metallurgy (P/M) route starting from 304L, which is a pre-alloyed austenitic stainless steel powder by controlled addition of alloying elemental powders. Prepared mixes are then green compacted at 550 and 650 MPa and then sintered under vacuum atmosphere. Sintering is performed at 1200 and 1250 ${}^{\circ }$C for 60 min with two cooling rates 5 and 20 ${}^{\circ }$C/min. Optical microscope and scanning electron microscope (with EDS) have been used for microstructural studies. Mechanical properties such as hardness, ultimate tensile strength and elongation (%) are measured using a Vickers hardness tester and tensile testing machine. The wear test is conducted using standard pin-on-disc apparatus, and the results are evaluated by a weight loss method. The compaction pressure, sintering temperature and rate of cooling are the parameters taken for the present study. Microstructure, mechanical properties and wear rate of the sintered P/M compacts are also studied.