Two general groups are identi"ed; those in which the individual processes complement each other and the combined e!ects result P.J. Kelly, R.D. Arnell / Vacuum 56 (2000) 159}172 169 Fig. 17. Ball-on-wheel wear test results for untreated, PVD TiN coated,plasma nitrided and duplex treated En40B steel (after Ref. [14]). Fig. 18. The design philosophy behind obtaining improved properties through duplex surface engineering processes (after Ref. [14]).
from both processes (group 1), and those where one process supplements, or reinforces the other, acting as
a pre-, or post-treatment, and the resultant properties are mainly related to one process (group 2). Examples from
both groups of process are given in Refs