Mechanical and interfacial characterization of laser welded Co-Cr alloy with different joint configurations.
OBJECTIVE
The mechanical and interfacial characterization of laser welded Co-Cr alloy with two different joint designs.


METHODS
Dumbbell cast specimens (n=30) were divided into 3 groups (R, I, K, n=10). Group R consisted of intact specimens, group I of specimens sectioned with a straight cut, and group K of specimens with a 45° bevel made at the one welding edge. The microstructure and the elemental distributions of alloy and welding regions were examined by an SEM/EDX analysis and then specimens were loaded in tension up to fracture. The tensile strength (TS) and elongation (ε) were determined and statistically compared among groups employing 1-way ANOVA, SNK multiple comparison test (α=.05) and Weibull analysis where Weibull modulus m and characteristic strength σο were identified. Fractured surfaces were imaged by a SEM.


RESULTS
SEM/EDX analysis showed that cast alloy consists of two phases with differences in mean atomic number contrast, while no mean atomic number was identified for welded regions. EDX analysis revealed an increased Cr and Mo content at the alloy-joint interface. All mechanical properties of group I (TS, ε, m and σο) were found inferior to R while group K showed intermediated values without significant differences to R and I, apart from elongation with group R. The fractured surfaces of all groups showed extensive dendritic pattern although with a finer structure in the case of welded groups.


CONCLUSIONS
The K shape joint configuration should be preferred over the I, as it demonstrates improved mechanical strength and survival probability.
Department of Biomaterials, School of Dentistry, National and Kapodistrian, University of Athens, Greece. ; Department of Dental Technology, Technological Educational Institution of Athens, Greece.
John
J
Kokolis
Department of Conservative Dentistry, University of Mosul, Iraq.
Makdad
M
Chakmakchi
Cork University Dental School and Hospital, University College Cork, Ireland.
Antonios
A
Theocharopoulos
Department of Dental Technology, Technological Educational Institution of Athens, Greece.
Anthony
A
Prombonas
Department of Biomaterials, School of Dentistry, National and Kapodistrian, University of Athens, Greece.
Spiros
S
Zinelis
Co-Cr alloys; Laser welding; Mechanical properties; SEM/EDX