对表面预置铬粉的铸态半高速钢进行超声冲击处理，再进行450℃×2 h退火处理，研究了处理前后其表层的显微组织与高温（400℃）耐磨性能。结果表明：铸态试验钢的组织由索氏体和碳化物组成，经超声冲击+退火处理后，索氏体中的渗碳体片断裂、球化，表层组织细化。经超声冲击+退火处理后，试验钢的表面硬度提高，表层硬度呈梯度分布，强化层厚度达2.5 mm；高温耐磨性能提高，磨损率由铸态的0.997 mg·min^-1下降到0.640 mg·min^-1，摩擦因数由铸态的0.547下降到0.509，磨粒磨损程度减轻。

Ultrasonic impact treatment was conducted on as-cast semi-high speed steel with surface presetting chrome powder, and then the steel was annealed at 450℃ for 2 h. The microstructure and high-temperature (450℃) wear resistance of the surface layer before and after treatment were studied. The results show that the as-cast structure of the tested steel consisted of sorbite and carbides. After ultrasonic impact and annealing treatment, the cemetite lamellae in sorbite was broken and spherized, and the structure of the surface layer was refined. After ultrasonic impact and annealing treatment, the surface hardness of the tested steel increased, the hardness in the surface layer distributed in gradient, and the thickness of the hardening layer reached 2.5 mm. Moreover, the high-temperature wear resistance was improved; the wear rate decreased from the as-cast 0.997 mg·min^-1 to 0.640 mg·min^-1, the friction coefficient decreased from the as-cast 0.547 to 0.509, and the abrasive wear degree also decreased.