Vacuum carburising

Vacuum carburising has reached industrial maturity with the development of vacuum furnaces and controls capable of gas carburising and quenching the carburised components using oil or pressurised inert gas. Due to their highly controllable heating rates and the availability of high carburising temperatures (950/1030°C), vacuum processes are finding an economic application for medium and deep case treatments. These methods have the advantage that treated components remain stationary throughout the process and the risks of component damage due to movement of hot components are eliminated. The surface and case chemistry can be very closely controlled, as can case depths, to within very tight limits and, as with all vacuum processes, treated components are kept clean. Savings can therefore be made in post heat treatment finishing operations, which more than offset the slightly higher treatment costs of these carburising methods. Whilst there is a need for careful tailoring of the process parameters for each design of component to be treated, the vacuum methods provide for much closer control of case depth range, uniformity and case chemistry than the other case hardening methods.