The stress corrosion characteristics of 18 wt-%Ni (MDN-250) maraging steel and its weldments made under different welding conditions have been investigated. The threshold stress intensity factor KISCC in stress corrosion conditions has been determined in 3.5 wt-%NaCl environment for the base metal and weldments. The fractured surfaces were analysed to study the types of fracture during stress corrosion cracking in base and weld metals. Fracture toughness tests were carried out and the results obtained from these tests have been compared with KISCC values.

Suresh Krishnamoorthy Seshadri

Vellore Margabandhu Radhakrishnan

Kudli Jatavallabha Lakshminarayana Iyer

Fracture

Fracture toughness

Stress corrosion cracking

Welding

Weldments

Maraging steel

Metal

Sodium chloride

Steel

article

corrosion

geometry

Iron and steel industry

mechanical stress

structure analysis

surface property

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IIT Madras

Stress corrosion cracking of maraging steel weldments

Materials Science and Technology

Austenite reversion in 18% Ni maraging steel and its weldments

Slow strain rate testing of notched cylindrical specimens of 18Ni2400 maraging steel has been carried out in air with 30% relative humidity and synthetic seawater environments. Peak-aged condition has been chosen, considering the relevance to engineering applications. Studies have also been carried out with different notch geometries to understand the effect of stress concentration factor. It is concluded from the study that (i) degree of stress concentration at the notch influences the notched tensile strength (ii) mild hydrogen embrittlement seems to occur in air environment, (iii) synthetic seawater environment drastically brings down the notched tensile strength and time to fracture (iv) environmentally assisted cracking occurs in air tests in quasicleavage and microvoid coalescence modes and in seawater tests in intercrystalline mode. © 2009 Elsevier Ltd. All rights reserved.

Corrosion Science

Environmentally assisted cracking of 18%Ni maraging steel

Gas tungsten arc welding was performed on 18Ni (250 grade) maraging steel sheet using two different filler wires: one of the same composition as the base material and the other containing more cobalt and aluminium and less molybdenum and titanium. Weld specimens were then aged under four different sets of conditions. After metallographic characterisation, mechanical properties including hardness, tensile strength and ductility, and fracture toughness were evaluated. Results showed that use of the matching filler material led to lower strength but higher ductility than in the other case; this was attributed to the presence of reverted austenite in the former (caused by segregation, especially of molybdenum) at the fusion zone substructure boundaries. In both types of weld metal, a re-solution treatment followed by aging at 480° C resulted in optimum tensile properties. Fracture toughness of the aged weldments was in general close to that of the parent material aged at 480° C; some deterioration occurred only when welds with pronounced segregation were made at high temperature.

Science and Technology of Welding and Joining

Tensile properties and fracture toughness of 18Ni (250 grade) maraging steel weldments

Sheet material specimens from 18Ni (250-grade) maraging steel were gas tungsten-arc welded using two different filler wires: one matching the base material in composition and the other with higher cobalt but lower molybdenum and titanium contents. Welding was carried out both in constant-current and pulsed modes. Post-weld aging was performed at three different temperatures, viz., 425, 480 and 520°C. Metallographic characterization revealed pronounced segregation, presumably of Ti and Mo, along interdendritic and intercellular boundaries in the weld metal produced with filler of matching composition. This led, during subsequent aging, to austenite reversion at temperatures much lower than in wrought (unwelded) material. Segregation and austenite reversion were not noticed when Ti and Mo contents were reduced in the filler wire, except at the highest aging temperature used. The use of pulsed welding resulted in some grain refinement, but the effect was not considerable. © 2000 Elsevier Science S.A.

Materials Science and Engineering A

Microstructural changes during welding and subsequent heat treatment of 18Ni (250-grade) maraging steel

Effect of hydrogen environment on the notched tensile properties of T-250 maraging steel annealed by laser treatment

International Journal of Fatigue

Fatigue resistance of steelsBoardman, B. Metals Handbook 10th Edn (ASM International, Materials Park, Ohio, 1990) Vol. 1, pp 673–688

Journal	Materials Science and Technology
ISSN	02670836
Open Access	No