Abstract
The objective of this work is to compare chromium electroplated from a hexavalent bath,
Cr
(+6)
,
with a more environmentally friendly process; nitrogen plasma source ion implantation of chromium from a trivalent bath
Cr
(+3)
which transforms it into a material that is harder than as-deposited
Cr
(+6)
with equal or better wear resistance properties. As-deposited, the hardness of a
Cr
(+6)
layer is higher (1200–1500 Knoop) than that of an as-deposited
Cr
(+3)
layer (950–1100 Knoop). Nitrogen-ion implantation at 120 kV to a dose higher than
3×10
17
N/cm
2
increases the hardness of the
Cr
(+3)
to 2300 Knoop. Wear resistance measurements show that under the same wear conditions a N-ion-implanted
Cr
(+3)
layer has about twice the wear resistance than the as-deposited
Cr
(+3)
and
Cr
(+6)
layer. Specifically, the width of the wear groove in a pin-on-disk test of an implanted
Cr
(+3)
plated layer is 60 μm for a 100 g load while for an as-deposited
Cr
(+6)
under the same load, the groove width is 114 μm. In this report we also demonstrate that nitrogen ion implantation into trivalent-deposited
Cr
(+3)
achieves the same chromium nitride phases and hardness as nitrogen-implanted
Cr
(+6)
.