Strengthening Ceramics through shot Peening

摘要

Lift off! When a space shuttle takes off, high-pressure turbo-pumps funnel over seventy kilograms of liquid hydrogen and almost half a ton of liquid oxygen per second into each of the three main engines. At a temperature of 250 deg C, the metallic parts in contact with the hydrogen fuel are subjected to extremely stressful conditions. Until now, it was necessary to dismantle and service the pump bearings after every single flight. But this is changing - the new parts are expected to survive at least twelve launches before they need servicing. Why? Because components consist of a hard ceramic material, silicon nitride. As researchers at the Fraunhofer Institute for Mechanics of Materials (IWM) in Freiburg, Germany have discovered, it is now possible to improve the strength properties of ceramic materials through "shot peening", a traditional metalworking technique. Similar to sandblasting, bombarding a metal surface with tiny metal balls causes it to become more dense and resistant -whereas ceramics subjected to the same treatment crack or fracture. For this reason, neither shot peening nor roiling are normally used on materials in this category.