The mechanical properties of nickel-chromium alloy welded by nd:YAG laser apparatus in dentistry

To investigate the optimum parameters and mechanical properties of nickel-chromium alloy welded by laser, different laser irradiation power was used to weld dental nickel-chromium alloy by Nd: YAG apparatus. Mechanical properties, metallographic evaluation and scanning electron microscopy (SEM) analysis were used to evaluate joined samples. The mechanical properties, including tensile strength, percentage elongation and Vickers microhardness, were compared with parent samples. The results showed that mechanical properties can be improved simply by increasing the irradiation power. Tensile strengths of joined samples irradiated by laser at 10.5 Joules were similar to that of the original metal. No statistically significant difference was found between joints fused at 10.5 Joules and the parent metal (p >; 0.05). Compared with original metal, the elongation values of joined samples decreased significantly (p <; 0.01). The microhardness values increased in the welded joint region. SEM observation on fracture surface revealed that the most penetration depth was 0.9mm to 1.0mm. No porosities and cracks and other defects were found. So laser is the more suitable technique in dentistry because of its stronger welded joints and smaller heat-affected zone and greater penetration depth.