Tensile Fracture Behavior of 316L Austenitic Stainless Steel Manufactured by Hot Isostatic Pressing

Abstract

Herein we investigate how the oxygen content in hot isostatically pressed (HIP'd) 316L stainless steel affects the mechanical properties and tensile fracture behavior. This work follows on from previous studies, which aimed to understand the effect of oxygen content on the Charpy impact toughness of HIP'd steel. We expand on the work by performing room-temperature tensile testing on different heats of 316L stainless steel, which contain different levels of interstitial elements (carbon and nitrogen) as well as oxygen in the bulk material. Throughout the work we repeat the experiments on conventionally forged 316L steel as a reference material. The analysis of the work indicates that oxygen does not contribute to a measureable solution strengthening mechanism, as is the case with carbon and nitrogen in austenitic stainless steels (Werner in Mater Sci Eng A 101:93-98, 1988). Neither does oxygen, in the form of oxide inclusions, contribute to precipitation hardening due to the size and spacing of particles. However, the oxide particles do influence fracture behavior; fractography of the failed tension test specimens indicates that the average ductile dimple size is related to the oxygen content in the bulk material, the results of which support an on-going hypothesis relating oxygen content in HIP'd steels to their fracture mechanisms by providing additional sites for the initiation of ductile damage in the form of voids.

Evolution of Non-metallic Inclusions Through Processing in Ti-V Microalloyed 316L and Al-V Microalloyed 17-4PH Stainless Steels for Hipping Applications

“…[3,31] The oxygen content in the 316L steel was 23 wt ppm in the forged material and ranged from 100 to 190 wt ppm in the HIP'd samples. [4,5] These values were lower than those in the powder and HIP'd steels of the present investigation, where purposefully enhanced oxygen contents in the powders, from storage and handling, were carried through into the HIPd product to assess the non-metallic inclusions through processing. The grain boundary characterization and grain size in gas-atomized 316L austenitic stainless steel powders-AMGA (sieved to 25 to 45 and < 150 lm) and VIGA (sieved to 106 to 150 lm) and after HIP product fabrication-have been presented separately.…”

“…[1] Recently, several investigations have highlighted the potential of HIP'd 316L steel for the fabrication of pressure retaining components for nuclear reactors. [2][3][4][5] Growth in the powder metallurgy sector [6][7][8][9][10][11][12] has led to a considerable increase in the complexity of alloys, products, and processing routes, in particular the metallic powder supply chain. [13] One of the main factors to take into consideration in metallic powders is that most steel alloying elements such as Cr, Mn, Ti, V, Si, and Al are highly reactive to oxygen when exposed to air or other oxygen containing atmospheres and can spontaneously oxidize even under high vacuum conditions.…”

“…Cooper et al [3][4][5]31] conducted comparative studies between forged and HIP'd 304L and 316L steels. The oxygen content in the 304L steel was 15 wt ppm in the forged material compared with 110 wt ppm in the powder sample and 120 wt ppm in the HIP'd sample.…”

Case Study of the Tensile Fracture Investigation of Additive Manufactured Austenitic Stainless Steels Treated at Cryogenic Conditions

“…Fracture analysis was carried out by field-emission scanning electron microscope (FE-SEM; Zeiss EVO) (Zeiss, Oberkochen, Germany) equipped with energy dispersive X-ray analysis (EDS) (Oxford Instrument, Abingdon-on-Thames, UK). The average size of dimples was evaluated by means of the linear intercept method (according to ASTM E112-96) [26,27]. Different areas were identified as the fracture surface, the sum of which is considered to be representative of the investigated material, by measuring microstructural features on different micrographs.…”

“…Thames, UK). The average size of dimples was evaluated by means of the linear intercept method (according to ASTM E112-96) [26,27]. Different areas were identified as the fracture surface, the sum of which is considered to be representative of the investigated material, by measuring microstructural features on different micrographs.…”