TITLE:
Experimental Investigation of Laser Surface Hardening of AISI 4340 Steel Using Different Laser Scanning Patterns
AUTHORS:
Baha Tarchoun, Abderrazak El Ouafi, Ahmed Chebak
KEYWORDS:
Laser Surface Hardening Process, Experimental Investigation, Laser Scanning Patterns, AISI 4340 Steel, Hardness Profile, Hardened Depth, Hardened Width, Design of Experiment, Analysis of Variance
JOURNAL NAME:
Journal of Minerals and Materials Characterization and Engineering,
Vol.8 No.2,
March
10,
2020
ABSTRACT: Laser
surface transformation hardening becomes one of the most modern processes used
to improve fatigue and wear properties of steel surfaces. In this process, the
material properties and the heating parameters are the factors that present the
most significant effects on the hardened surface attributes. The control of
these factors using predictive modeling approaches to achieve desired surface
properties leads to conclusive results. However, when the dimensions of the
surface to be treated are larger than the cross-section of the laser beam,
various laser-scanning patterns are involved. This paper presents an
experimental investigation of laser surface hardening of AISI 4340 steel using different
laser scanning patterns. This investigation is based on a structured
experimental design using the Taguchi method and improved statistical analysis
tools. Experiments are carried out using a 3 kW Nd: YAG laser source in order
to evaluate the effects of the heating parameters and patterns design
parameters on the physical and geometrical characteristics of the hardened
surface. Laser power, scanning speed and scanning patterns (linear, sinusoidal,
triangular and trochoid) are the factors used to evaluate the hardened depth
and the hardened width variations and to identify the possible relationship
between these factors and the hardened zone attributes. Various statistical
tools such as ANOVA, correlations analysis and response surfaces are applied in
order to examine the effects of the experimental factors on the hardened
surface characteristics. The results reveal that the scanning patterns do not
modify the nature of the laser parameters’ effects on the hardened depth and
the hardened width. But they can accentuate or reduce these effects depending
on the type of the considered pattern. The results show also that the
sinusoidal and the triangular patterns are relevant when a maximum hardened
width with an acceptable hardened depth is desired.