  Plasma Surface Metallurgy/Alloying is a kind of surface metallurgy/alloying
to employ low temperature plasma produced by glow discharge to diffuse alloying
elements into the surface of substrate material to form an alloy layer. The
first plasma surface metallurgy technology is plasma nitriding invented by
German scientist Dr. Bernard Berghuas in 1930. He was the first person to apply
glow discharge to realize the surface alloying. In order to break the
limitation of plasma nitriding technology, which can only be applied to a few
non-metallic gaseous elements such as nitrogen, carbon, sulfur, the "Double
Glow Discharge Phenomenon"was found in 1978. Based on this phenomenon the
"Double Glow Plasma Surface Metallurgy Technology", also known as the "Xu-Tec
Process" was invented in 1980. It can utilize any chemical elements in the
periodic table including solid metallic, gas non-metallic elements and their
combination to realize plasma surface alloying, hence greatly expanded the
field of surface alloying. Countless surface alloys with high hardness, wear
resistance and corrosion resistance, such as high speed steels, nickel base
alloys and burn resistant alloys have been produced on the surfaces of a
variety of materials. This technology may greatly improve the surface
properties of metal materials, comprehensively improve the quality of
mechanical products, save a lot of precious alloy elements for human beings.
Based on the plasma nitriding technology, the Xu-Tec Process has opened up a
new material engineering field of "Plasma Surface Metallurgy". This Review
Article briefly presents the history of glow discharge and surface alloying,
double glow discharge phenomenon, basic principle and current status of Double
Glow Plasma Surface Metallurgy/Alloying. Industrial applications, advantages
and future potential of the Xu-Tec process are also presented.
