Application of active powders at fluidised bed heat treatment technologies

摘要

The paper describes the principles and conditions of carrying out of a new type of fluidised bed thermo-chemical treatment in chemically active powders with different ways of fluidisation. These new fluidised bed thermo-chemical treatments in chemically active powders are primarily for the formation of surface diffusion layers on parts made of constructional and tool steel. This method can be used for sherardising, alitising, carbonitriding, nitrocarburising, carburising or boronising. Characteristics of chemically active powders are compared with the chemically inert powders, used in conventional fluidised bed treatments. In addition, the paper presents the feasible ways to use fluidisation by gas flow or by mechanical vibrations for different processes and their main stages, i.e., heating up to treatment temperature, soaking at treatment temperature and cooling down after the soaking. Advantages and disadvantages of these processes, in comparison with the conventional methods of fluidised bed thermo-chemical treatment, are given.