The importance of heat treating nickel based alloys used in fixed prostheses technology

Ni-Cr alloys used in dental technology belong to the precipitation hardened alloys and their mechanical properties are developed by heat treatment. The purpose of the study was to evaluate the effect of heat treatments on microplasma welded Ni-Cr alloys with different composition used in dental technology, by metallographic analyses and microhardness tests. For the experimental study 16 plates were cast conventionally. Half of them were coold slowly at room temperature and half quickly, quenching them in cold water. The plates were matched and welded using microplasma Welder. Half of the welded specimens were heat treated using a furnace 60 min at 800°C and then cooled uniformly to room temperature. They were analyzed metallographic, and the microhardness was determined in the base metal (BM), weld metal (WM) and heat affected zone (HAZ). The cracks and the modification of the microstructure due to the rapid heating and solidification process can be a real problem and affect the quality of the weld. Even the chemical composition of the alloys was similar; their behavior at heat treatment was different. Therefore it is important that the heat treatments procedures be particularized for each alloy type. Keywords: Ni-Cr alloys, heat treatment, prostheses technology