G0301505 Effect of the Primary Carbide on Rotating Bending Fatigue Strength of Cold Work Tool Steels

Abstract

SKD11 contains many coarse carbides to improve wear resistance and hardness. However fatigue strength of SKD11 decreased due to coarse carbides. Therefore new SKD11 was developed for improving adhesion to surface coating and less primary carbide than SKD11. Rotary bending fatigue test in air at room temperature using hourglass shaped specimen is conducted to clarify S-N property and effect of the carbide on fatigue strength of cold work tool steels. From the experimental results of fatigue test, it was found that the fatigue strength of improved showed high values in the range from 10^4 to 10^7 cycles than that of JIS SKD11. Fatigue strength was increased 220〜240 MPa in low cycle and 250〜260 MPa in high cycle, significant difference in fatigue strength was observed in high cycle. From the results of fracture surface observation by SEM and EDX, it was found that fracture origin of JIS SKD11 was internal coarse carbide. Fracture origin of new SKD11 was surface.