Erosion is vitally important in aerospace and petrochemical industries, especially when the targets such as flight engines, gas control valves etc are subjected to high speed in an environment containing sand particles. A new erosion test rig, with a capability of producing a velocity greater than Mach 3, was built up to cater to this purpose. Results obtained from stainless steel testing showed that erosion rate was saturated at 120. s and reduced subsequently. In addition, the results of erosion rates at different impact angles indicated that severe erosion maximizes at an impact angle of 40°. Further, erosion profiles showed different erosion effects on the sample surface. Surface roughness increased with respect to time and peaked at 45°. Investigation into surface microstructure revealed different erosion mechanisms associated with different impact angles. The erosion mechanism transition from micro-plowing to indentation induced plastic deformation took place from low to high impact angles. Further, computational fluid dynamic model was used to compare with experimental results.