Fig. 26 A 4140 grade steel seamless tubing that failed because of quench cracks. (a) Cross section of tube showing extensive cracking revealed by dye-penetrant inspection. (b) SEM micrograph showing intergranular fracture at a crack origin. Original magnification: 90×. (c) SEM micrograph More

Fig. 6 Fracture surfaces of SAE 4140 impact testpieces. Tested at room temperature, right, and at –196°C, left More

Fig. 6 Microhardness traverses across a nitrided case on 40HM (4140)-grade steel. 1, tempering temperature 550 °C, time 4 h; 2, tempering temperature 550 °C, time 16 h; 3, tempering temperature 620 °C, time 4 h; 4, tempering temperature 620 °C, time 16 h More

Fig. 9 Location of fatigue crack initiation on nitrided 40HM (4140)-grade steel. Original magnification: 100× More

Fig. 34 View of the identified seam defects in a bar sample of AISI 4140. Unetched. Original magnification: 100× More

Fig. 23 Impact values of 4140 specimens after various types of tempering treatments. Source: Adapted from Ref 42 More

Fig. 9.44 Austenitization curves for the steels (a) 42CrMo4 (AISI 4140) and (b) 100Cr6 (AISI 52100). Source: Ref 13 , 50 More

Fig. 10.10 AISI 4140 steel bar with a cylindrical insert of AISI 8640 steel subjected to austenitization in hydrogen atmosphere at 1120 °C (2050 °F) and isothermally treated at 650 °C (1200 °F). Treatment was sufficiently long to transform the steel AISI 4140 to ferrite and pearlite, followed More

Fig. 3.43 Stress-corrosion resistance and fracture toughness of AISI 4130 and 4140 steels. Source: Ref 3.6 More

Fig. 8.12 Time-temperature-austenitizing diagram for 42CrMo4 (SAE 4140) steel. Source: Ref 8.20 More

Fig. 9.21 Variations in Mn and C concentrations across a quench-and-tempered 4140 steel bar, 95.25 mm (3.75 in.) in diam, and containing nominally 0.40% C and 1.0% Mn. Electron microprobe analysis. Courtesy of J. Black. Source: Ref 9.59 More

Fig. 10.4 Cooling transformation diagram (heavy lines) for 4140 steel. Also shown are Jominy end-quench data and isothermal transformation diagram (light lines). Source: Ref 10.5 More

Fig. 16.31 Jominy end-quench curves for 4130 (top), 4140 (middle), and 4150 (bottom) steels each with low (0.002 %) and high (0.018 %) levels of phosphorus. Source: Ref 16.49 More

FIG. 5.7 Hardenability curve for SAE 4140 steel. More

Fig. 9 Debonding of a MnS particle in a 4140 quenched and tempered steel due to a bending stress. The component was forged, and considerable directionality (banding and fibering) existed in the material. Crack propagation from bottom to top in the photograph. Courtesy of M. West, University More

Fig. 15 4140 steel, oil quenched from 845 °C (1550 °F), tempered 2 h at 620 °C (1150 °F), surface activated in manganese phosphate, and gas nitrided 24 h at 525 °C (975 °F). Structure is white layer of Fe 2 N, Fe 3 N, and Fe 4 N, and tempered martensite. 2% nital. 400× More

Fig. 18 4140 steel, quenched and tempered to 30 HRC, then ion nitrided 24 h at 510 °C (950 °F). Monophase surface layer of Fe 4 N, plus a diffusion zone of nitride containing tempered martensite. Nital. 750× More

Fig. 18 Microhardness traverse of AISI 4140 steel gear sample More

Fig. 42 Fatigue fracture of AISI 4140 bull gear due to improper heat treatment. The one-of-a-kind replacement gear had a service life of just 2 weeks. Heat treatment did not produce full hardness in gear teeth. Hardness at tooth face, 15 HRC; at tooth core, 82 HRB. (a) Outside diameter of gear More

Fig. 43 Structure of fractured tooth from AISI 4140 bull gear in Fig. 42 . (a) Tooth cross section. Arrows show depth to which temperature exceeded Ac 1 during heat treatment. (b) Near-surface hardened region of tooth. Large ferrite indicates that complete austenitization was not obtained More