A New Method to Study the Thermal Fatigue Resistance of Molybdenum by High Power Laser Irradiation

In single roll rapid quenching molding, especially for the preparation of amorphous ribbons and rare earth permanent magnetic materials, the chilling roll is an extremely important component of the preparation equipment. However, frequent repair of the roll is not conducive to continuous large-scale production because of its poor thermal fatigue resistance. Molybdenum is gradually being used as chilling roll material in some applications, and in the present paper a new approach to study the thermal fatigue resistance of molybdenum is based on laser pulse irradiation on the molybdenum surface. A new designed device effectively prevents the molybdenum to be oxidized during the laser heating test. The experiments of thermal fatigue damage on molybdenum were conducted by the high power laser. The results shows that the fatigue cracks had been propagated in the irradiated region after the specimen was loaded by 200 times pulsed laser heating. There is a greater crack density in the laser heating brim region than in the center of the irradiated region. According to the transgranular mode of crack propagation in the laser heating brim region and intergranular mode in the center of the irradiated region, the maximum stress took place at the intersection region due to the great temperature gradient in the laser heating brim region. Continued basis-oriented experiments are planned, regarding the mechanism of thermal fatigue crack initiation and propagation for chilling roll materials.