Effect of Hydrogen on the Static Crack Resistance of 05Kh13N8M3 Cast Martensitic Steel

Abstract

The laws governing the influence of a hydrogen atmosphere at a pressure of up to 15 MPa with controlled total oxygen and water vapor content of up to 0.004 g/m³ and pre-absorbed hydrogen on the strength and ductility characteristics, short-term and long-term static crack resistance of 05Kh13N8M3 cast martensitic steel (in wt.%: 0.045 C, 0.38 Si, 12.9 Cr, 2.69 Mo, 0.43 Mn, 7.8 Ni, 0.057 La) at room temperature were studied. After hydrogen pre-charging for 4 h at a temperature of 773 K and a pressure of 5, 10, and 15 MPa, the hydrogen content of the specimens determined with a LECO TCH 600 device by infrared adsorption with melting was 3.3, 4.9, and 7.6 ppm, respectively. It was found that under short-term loading, the intensity of the effect of hydrogen on the fracture toughness of steel increases with an increase in the absorbed hydrogen content, crack sharpness, and a decrease in the loading rate. At the maximum hydrogen concentration of 7.6 ppm and a tensile rate of 0.1 mm/min, the relative elongation, lateral contraction ratio of smooth 25 mm long cylindrical specimens with a test portion diameter of 5 mm and the critical stress intensity factor of beam specimens measuring 20×10×100 mm with a relative length of the pre-induced crack of \(\upvarepsilon =\) 0.53 decrease almost twofold. At the same concentration, hydrogen does not affect the stress intensity factor of cracked specimens at a rate of 10 mm/min and specimens with a stress concentrator in the form of a notch with a tip radius of 0.065 mm at a rate of 0.1 mm/min. Under long-term static loading with a test duration of 300 h of double-cantilever beam specimens in the form of a rectangular plate 10 mm thick with milled grooves 3 mm deep and a tip angle of 60°, the threshold value of the stress intensity factor decreases. The rate of subcritical crack growth in the second portion of the hydrogen cracking diagram increases in proportion to the logarithm of hydrogen concentration.