The authors present a new generation of surface processings for cold f
orging of steels. These coatings, designed to replace phosphatation, a
re easy to implement and less polluting. A drawing-seizure test proced
ure is also proposed to evaluate the tribological performances of thes
e new coatings more objectively and to compare them to standard zinc p
hosphatation. Test results, including the occurrence of boundary lubri
cation, mixed lubrication and seizure at the slider-coated specimen in
terface, are related to effective bonding and to lubricant effects of
the coatings. The new surface processes concern two types of chemicals
: a boron salts-based processing (sodium tetraborate: B4O7Na2.5H(2)O a
nd derivatives) and a new generation of silicate-based processings rec
ently developed to comply to environmental constraints. The seizure re
sistance of the coatings is mainly analyzed by considering different p
rocessing conditions such as bath temperature and drying conditions. T
his parameter, which is very sensitive to treatment parameters, has gi
ven rise to an easy and objective optimization of the new surface proc
essings. It has been shown that the silicate-based processing presents
characteristics very close to those of phosphatation. This new genera
tion of coatings could therefore replace phosphatation for severe cold
forging operations in the short term. (C) 1998 Elsevier Science S.A.