Microstructure and mechanical behavior of 316L liquid phase sintered stainless steel with boron addition

摘要

This work focuses on the role of boron as a sintering additive in powder metallurgy processing of the AISI 316L austenitic stainless steel. Boron effect was investigated regarding densification, microstructure, hardness and micro-scale abrasion resistance. Samples were prepared with 0.6 wt% and 0.8 wt% of boron and sintered at 1240 degrees C. The microstructure of the sintered bodies was characterized by field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), and Rietveld refinement of X-ray diffraction (XRD) patterns. Differential scanning calorimetry (DSC) was used to study the behavior of both the free and boron-containing 316L samples at solid and liquid states. The hardness of austenitic matrix and precipitated borides was determined by instrumented indentation tests, EDS and XRD results revealed the formation of M-23(B,C)(6) carboboride and hard M2B borides, which were concentrated mainly in intergranular sites. The formation of M2B borides favored material densification through the development of a liquid phase during sintering, promoting an increase in density, hardness and micro-scale abrasion resistance of the AISI 316L steel.