TITLE:
Laser Surface Hardening of Tool Steels—Experimental and Numerical Analysis
AUTHORS:
Abdel-Monem El-Batahgy, Ramadan Ahmed Ramadan, Abdel-Rahman Moussa
KEYWORDS:
High Speed Tool Steels; Laser Surface Hardening; Ashby and Easterling Heat Transfer Equations; Design Expert Software; Laser Processing Charts
JOURNAL NAME:
Journal of Surface Engineered Materials and Advanced Technology,
Vol.3 No.2,
April
30,
2013
ABSTRACT: This research work is focused on both
experimental and numerical analysis of laser surface hardening of AISI M2 high
speed tool steel. Experimental analysis aims at clarifying effect of different
laser processing parameters on properties and performance of laser surface
treated specimens. Numerical analysis is concerned with analytical approaches
that provide efficient tools for estimation of surface temperature, surface
hardness and hardened depth as a function of laser surface hardening
parameters. Results indicated that optimization of laser processing parameters
including laser power, laser spot size and processing speed combination is of
considerable importance for achieving maximum surface hardness and deepest hardened zone. In
this concern, higher laser power, larger spot size and lower processing speed
are more efficient. Hardened zone with 1.25
mm depth and 996 HV surface hardness was obtained using 1800 W
laser power, 4 mm laser spot size and 0.5 m/min
laser processing speed. The obtained maximum hardness of laser surface treated
specimen is 23% higher than that of conventionally heat treated specimen. This
in turn has resulted in 30% increase in wear resistance of laser surface treated specimen. Numerical
analysis has been carried out for calculation of temperature gradient and
cooling rate based on Ashby and Easterling equations. Then, surface hardness
and hardened depth have been numerically estimated based on available Design-Expert
software. Numerical results indicated that cooling rate of laser surface
treated specimen is high enough to be beyond the nose of the CCT diagram of the
used steel that in turn resulted in a hard/martensitic structure. Numerically
estimated values of surface temperature, surface hardness and hardened depth as
a function of laser processing parameters are in a good agreement with
experimental results. Laser processing charts indicating expected values of
surface temperature, surface hardness and hardened depth as a function of
different wider range of laser processing parameters are proposed.