Effect of Temperature on the Fracture Toughness of Hot Isostatically Pressed 304L Stainless Steel

Abstract

Herein, we have performed J-Resistance multi-specimen fracture toughness testing of hot isostatically pressed (HIP'd) and forged 304L austenitic stainless steel, tested at elevated (300°C) and cryogenic (À 140°C) temperatures. The work highlights that although both materials fail in a pure ductile fashion, stainless steel manufactured by HIP displays a marked reduction in fracture toughness, defined using J 0.2BL , when compared to equivalently graded forged 304L, which is relatively constant across the tested temperature range.https://doi.org/10.1007/s11661-018-4466-x Ó The Author(s) 2018. This article is an open access publication Hot isostatic pressing (HIP) is a component manufacturing technique, which employs the use of high temperature, and isostatically controlled pressure to consolidate metal alloy power of desired chemistry into bulk metal under an inert (usually argon) atmosphere. [1] The advantages of HIP are well documented, [1][2][3][4] the most significant being within HIP's ability to produce near-net shape components; components with exceedingly complex geometries thus eliminating the need for subsequent machining/welding procedures on the manufactured component. This may not only reduced the costs associated with the overall manufacture process, but through the elimination of welded joints, produces components of homogenous metallurgy; omitting common issues associated with welding of components; hot cracking, different metallurgical zones, induced residual stresses, etc. This is clearly an advantage for components which will be subjected to high stress conditions throughout their lifetime. The degree of metallurgical homogeneity which HIP produces results in no grain directionality, like that commonly seen in forgings, due to the isostatically controlled pressure and temperature and therefore HIP materials display isotropic mechanical properties. Finally, HIP produces material with a comparatively smaller grain size than that of forgings and castings, which not only improves the yield strength and ultimate tensile strength, also lends itself to easier inspection view non-destructive examination techniques.Because of HIP's ability to increase design freedom, there have been increased efforts to demonstrate that components produced by HIP have equivalent or better material properties than those of equivalently graded forged materials. However, the authors have recently shown that the fracture behavior is subtly different between equivalently graded HIP and forged austenitic stainless steel, with HIP 304L and 316L exhibiting a reduction in impact toughness [5,6] as well as HIP 304L exhibiting a reduction in J-integral fracture toughness at ambient temperature. [7,8] This difference in fracture behavior was attributed to the presence of a comparatively large volume fraction of non-metallic oxide inclusions in the HIP microstructure, which lower the energy required to cause fracture via an unzipping effect, whereby ductile void growth is unable to occur on the same scale as in forged stainless steel...

Flow and fracture of austenitic stainless steels at cryogenic temperatures

“…Figure A.22: Comparison between the stress-strain curves obtained in this paper for AISI 304L and experimental results taken from the works ofYanushkevich et al (2017),Spencer et al (2004),Cooper et al (2018), DeMania (1995,Mei and Morris Jr (1990),Fultz and Morris Jr (1986),Behjati et al (2011), Ogata et al (1985 andOgata et al (1990). Data corresponding to tensile samples tested under quasi-static loading at different temperatures: (a) T = 300 K, (b) T = 77 K and (c) T = 4 K.…”

Flow and fracture of austenitic stainless steels at cryogenic temperatures

“…Moreover, the fracture tests data have been used to determine the crack-growth resistance J − R curves and the fracture toughness of the investigated materials using four different methods here referred to as ASTM Compliance Cooper et al (2018), DeMania (1995, Mei and Morris Jr (1990), Fultz and Morris Jr (1986), Behjati et al (2011), Ogata et al (1985 and Ogata et al (1990). Data corresponding to tensile samples tested under quasi-static loading at different temperatures: (a) T = 300 K, (b) T = 77 K and (c) T = 4 K. Wang et al (2008), Wang et al (2010), Botshekan et al (1997), Botshekan et al (1998), Obst and Pattanayak (1982), Pattanayak (1984), Czarkowski et al (2011), Park et al (2011 and Couturier and Sgobba (2000).…”

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

“…Note that, the level of residual Cu in powder 316L steel is not generally explicitly quoted in the literature [2][3][4]30,[66][67][68][69][70][71][72] and other powder stainless steels, [68] for example AISI 304L [31] and 304. [66] A few examples in which the level of residual Cu was reported are 0.05-0.06 wt pct in HIP'd 316L, [5] 0.05 wt pct Cu in a water-atomized 316L powder [30] and 0.2 wt pct Cu in a gas-atomized 316L steel powder [51] and <0.1 wt pct in a 304L powder.…”

“…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.…”

“…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. [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.…”