In conclusion it can be stated, based on the observations made, that:
• No significant inclusions or chemical composition changes were noted at any junction
• The microstructure appears finer, in all cases, in the junction area
• The interface area shows a slight discontinuity in the case of samples welded with a single pulse (with or without the use of argon)
• The samples welded with two pulses (with and without the use of argon) appear as morphologically contiguous and devoid of discontinuity at the interface
• The interface area appears, however, as markedly different in the case of the sample welded with two pulses without using argon, with evidence of an altered band, of about 50 microns, which surrounds the entire interface. This sample also has evidence of external oxidation (blue color)
• The use of the argon flow and two pulses is necessary to avoid the occurrence of external oxidation and of an altered band in the internal section in the junction area.
In conclusion, this sample presents a morphologically continuous junction free from alterations.
The method of punctual resistance welding, with inert atmosphere flow, applied to intraoral use, is therefore proposed as an effective method to obtain a junction with characteristics suitable for the purpose. The argon flow avoids oxidation without inducing the presence of gas porosity. The applied load and the temperature reached (by applying a double electric impulse) are sufficient to obtain a perfectly continuous joint.