Abstract
Recently, laser welding is used to connect metal frames instead of soldering in dentistry. However, the changes in the mechanical properties of the connecting area welded by laser irradiation are not clear. This study investigated the characteristics of the melting zone produced by laser irradiation in dental metals. As test materials, pure titanium, Co-Cr alloy and Au-Ag-Pd alloy were used. Board-shaped specimens were prepared by casting and a laser was irradiated to the surface of the specimens under various conditions. After laser irradiation, the diameter of the fusion zone produced by laser irradiation in the surface of the specimens and the depth of the fusion zone in the cross section of the specimens were measured with a stereomicroscope. Furthermore, the Vickers hardness in the fusion zone and in the original casting zone of the specimens were measured. In addition, cross sections of the specimens were observed with SEM and the distribution of components was analyzed with EPMA.
The results were as follows:
1. Under the same laser irradiation conditions, pure titanium showed the maximum values of diameter and depth of the fusion zone, followed by Co-Cr alloy and Au-Ag-Pd alloy in that order.
2. The Vickers hardness in the melting zone increased compared with that in the original casting zone in every test metal, however, Au-Ag-Pd alloy showed only a small change.
3. Cross-sectional images of the Co-Cr alloy and Au-Ag-Pd alloy showed an uneven distribution of metal components in the original casting zone, while the distribution was homogeneous observed in the fusion zone.
