A study of nickel-based corrosion resisting alloy layer obtained by doubleglow plasma surface alloying technique

En this paper, Ni-Cr-Mo-Nb multi-element surface alloying has been investig ated on a substrate of three kinds of industrial steels (industrial pure ir on, low carbon steel and 304 stainless steel) by means of the double glow p lasma surface alloying technique. The results showed that highly alloyed ni ckel-based surface alloying layers were formed on the surface of the three kinds of steels. The alloying layer was uniform, continuous and compact. Th e alloying layers consisted of a gamma phase or gamma matrix with several p recipitates (P or Laves phase, and NbC carbide, etc.). A method of eliminat ing these precipitates has also been discussed. The corrosion resistance of the nickel-based surface alloying layer was investigated by an electrochem ical method in a 3.5% NaCl and 5% HCl solution, and 200-h exposure tests in a 20% H2SO4 and 20% HCl solution. The corrosion resistance of surface allo ying layer formed on stainless steel substrate was better than that of the nickel-based alloy Inconel 625 and 304 stainless steel. The experimental re sults indicated that this is an effective way to obtain a high quality corr osion resisting surface alloying layer on the surfaces of steels using the double glow plasma surface alloying technique. (C) 2000 Elsevier Science B. V. All rights reserved.