2009)02-104-05
Camshaft is one of the key parts or components in
the engines of automobile and other vehicles. The
performance is to control the open and close intervals of the
inlet and exhaust poppet valves by its cams.
Due to the cyclic impact loading on the contacting surfaces
of the cam and the follower, it often gives rise to premature
wear of cam profile and affects a routine run of the valve
gear such as the rotational speed, valve displacement and the
torque. On the other hand, simultaneously the most serious,
under cyclic bending and torsion, fatigue fracture of camshaft
initiating at stress concentration easily occurs. Therefore it
demands the camshaft has not only excellent wear resistance
but also adequate anti-impact toughness [1-2].
Many researches on improving wear resistance of cam
and the follower by surface hardening have been reported
in recent decades [3-6]. The measures of surface hardening
include phase transformation such as surface chilling and heat
treatment, and precipitation processes occurring in the material
during surface thermochemical treatment by ion nitriding and
nitrosulphurizing or spraying of multicomponent layers and so
on
At present, almost all of camshafts are made of cast
iron (chilled cast iron, nodular cast iron, surface hardened,
and malleable cast iron, etc), steel (ion nitrided and
nitrosulphurized, hardened steel) and so on. Moreover, chilled
grey cast iron is commonly used worldwide for camshaft
production