METHOD OF FORMING A NITRIDE OR CARBONITRIDE LAYER

摘要

A nitride or carbonitride layer is formed on the surface of a metal material as follows: A treating agent composed of a refractory powder of alumina or the like and a powder of a metal for forming a nitride or a carbide or an alloy thereof is disposed in a fluidized bed furnace; the treating agent is fluidized to form a fluidized bed by introducing an inert gas; the fluidized bed furnace is heated to a temperature of not higher than 700.degree.C; an activator of a halogenated ammonium salt is intermittently supplied into the fluidized bed at a rate of 0.001 to 5 wt%/hour based on the total amount of the treating agent; and the metal material to be treated is disposed in the fluidized bed during or after any of the above steps. For example, a nitride layer composed of only a metal for forming a nitride which contains almost no Fe-N is formed on the surface of iron steel even at a temperature as low as not higher than 700.degree.C. The layer is very hard and efficient in wear resistance, and the toughness of the base metal is hardly lowered.