Metallurgical and Hydrogen Effects on the Small Punch Tested Mechanical Properties of PH-13-8Mo Stainless Steel

Abstract

PH13-8Mo is a precipitation hardened martensitic stainless steel, known for its high strength but also for its high sensitivity to hydrogen embrittlement. Small punch test, SPT (also referred to as the ball punch test, BPT), is a relatively simple and new technique to assess the mechanical properties of samples under biaxial loading conditions. The current study utilizes the unique loading conditions of SPT to investigate the mechanical behavior and fracture prior to and after the hydrogen charging of PH13-8Mo steel. The mechanical characteristics were investigated at different metallurgical conditions: solution and quenched (SQ); fully-aged (550 °C for 4 h) and over-aged (600 °C for 4 h). Samples were cathodically hydrogen charged in a 1 M H2SO4 solution containing NaAsO2 (0.125 mg/L) at 50 mA/cm2 for different durations of 0.5 h, 2 h, and 19 h, and compared to the as-heat-treated condition. A fractographic examination was performed following the SPT measurements by scanning electron microscopy (SEM). Transmission electron microscopy (TEM) and x-ray diffraction (XRD) analyses were used as complementary characterization tools. It is shown that upon hydrogen charging, the SPT fracture mode changes from ductile to completely brittle with a transition of mixed mode cracking also affecting the SPT load-displacement curve.

Recent Advances on Composition-Microstructure-Properties Relationships of Precipitation Hardening Stainless Steel

“…Advanced PHSS not only has a combination of ultra-high strength and acceptable toughness, but also the steel has certain anti-corrosion properties [ 99 , 100 ]. Additionally, the steels with excellent properties require the adjustment of the microstructure, especially in the formation of nano-precipitates.…”

Aging Effect on Microstructure and Machinability of Corrax Steel

“…The growth of reverted austenite into martensite reduced massive martensite to plate martensite. In addition, the Al content allows NiAl precipitations through aging which caused resistance to coarsening, even at high temperatures [23]. Maraging steels are designed to form a martensitic structure and austenite transforms completely into martensite during cooling [29][30][31][32].…”

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“…Due to these properties, PH 13-8 Mo steel is preferred for various applications such as aircraft and helicopter landing gear under high loads, rocket engine bodies, high-pressure containers, submarine bodies, and petrochemical equipment. [1][2][3] Machining is basically a chip formation process in which the excess material on the raw product is removed with the help of a cutting tool during production. Among the machining operations, turning operation is the oldest and most common method used.…”

“…Due to these properties, PH 13-8 Mo steel is preferred for various applications such as aircraft and helicopter landing gear under high loads, rocket engine bodies, high-pressure containers, submarine bodies, and petrochemical equipment. 1–3…”