|
To form a thin layer of vanadium or chromium carbide with an
ultra-hardness on the surface of steels, steels with various
carbon contents were heated in the borax bath containing the
powder of ferro-vanadium or chromium. The influence of process
conditions on the layer of carbide was studied through
examining the thickness, hardness, adhesion, wear-resistance,
microscopy and X-ray diffraction of the layer. The results
obtained were summarized as follows: 1. A thin layer of
vanadium carbide or chromium carbide with an ultra-hardness was
formed on the surface of the steels which were heated in a
borax bath containing the powder of ferro- vanadium or
chromium. 2. When the borax was melt under the nitrogen
atmosphere, the duration of the borax bath was increased. 3.
Increasing the weight ratio of V-Fe powder to the borax bath or
the temperature of the borox bath led to an increase in the
coating rate of the carbide layer, but the hardness of the
layer was decreased and the vacancy ratio was increased. 4. The
higher the carbon content of steels, the more rapid the growth
rate of the carbide layer and the longer the duration ofthe
borax bath. 5. The growth rate of the carbide layer increased
substantially if the steel was carburized before being heated
in the borax bath. 6. When the steel was carburized before
being heated in the borax bath, the higher the carbon potential
of carburizing system; the more rapid the growth rate of the
carbide layer. 7. The wear resistance of the steel coated a
layer of vanadium carbide was superior to those of both the
original steel and quenched steel by 10 and 6 times,
respectively.
|