Heating hot rolled feroous sheet in an open furnace to a temperature within the transformation range and then cooling in air, in order to soften the metal. The formation of a bluish oxide on the surface is incidential.
(Heat Treater's Guide: Practices and Procedures for Irons and Steels, Chandler H., Page #868)
Double Aging 26.03 14:11
Employment of two aging treatments to control the type of precipitate formed from a supersaturated matrix in order to obtain the desired properties. The first aging treatment, sometimes referred to as intermediate or stabilizing, is usually carried out at higher temperature than the second
(Principles of the Heat Treatment of plain carbon and low alloy steels, Brooks C.R., Page #472)
Double tempering 26.03 14:15
A treatment in which a quench-hardened ferrous metal is subjected to two complete tempering cycles, usually at substantially the same temperature, for the purpose of ensuring completion of the tempering reaction and promoting stability of the resulting microstructure.
(Principles of the Heat Treatment of plain carbon and low alloy steels, Brooks C.R., Page #472)
Diffusion Coating 26.03 14:25
Diffusion Coating processes have been applied for many years to improve the enviromental residence of a base alloy by enriching the surface in Cr, Al or Si. Diffusion Coatings be applied to hot-gas components using several techniques, including pack cementation, slurry cementation, and metallising. Fludised bed techniques can also be used to deposit diffusion coatings on a laboratory scale.
In the pack cementation process, components to be coated and buried in a pack contained in a sealed retort. The exact process cycle, time, and temperature are depended on the required coating, coating thickness and subsequent substrate heat treatment. The pack contains three elements 1-) a donor alloy that releases solute material at a known rate and hence determines the pack activity 2-) a halide activator that dissociates the process cycle and acts to transport solute material from the back to the component to be coated, and 3-) an inert oxide diluent prevent pack - sintering
(Physical Metallurgy Vol. 1 , Cahn W.R., Haasen P., pages #1345-1346)
No comments:
Post a Comment