Comparative study on the effect of adding chromium, molybdenum, and tungsten on the corrosion resistance of Cobalt-Nickel-Aluminum alloy

Nickel-titanium (NiTi) alloy has super-elasticity and shape memory. NiTi alloys are used in stents, staples, guide wires, orthodontic wires, and endodontic tools. But its disadvantage, which was discovered over time, led to various experiments to improve its efficiency. Raw materials used in this study: cobalt, nickel, aluminum, and titanium. All raw metal materials used in this research were in the form of pellets or balls with 99.9% purity. They had been supplied by Alpha Company Limited by means of sealed plastic bags of 3 kilograms each. Samples were divided into two main groups (group1 for Co-Ni-Al alloy and group2 for NiTi alloy). Raw cobalt, nickel, aluminum, and titanium materials were collected with purity of 99.99% and then weighted to achieve a chemical composition of Co36.4 Ni34.5 and Al29 for group1(chemical composition was used based on the previous work of (Arbilei 2013), and a composition of Ni56 Ti44 for group2 (Thompson 2000) with a total weight of 1.5 kilogram for each group to be melted in a vacuum induction melting furnace (model 913-FUR-03 idealvac) (Figure 8) and casted into rod like molds and investigated simultaneously. After examining the results of wear, fatigue, corrosion resistance, and hardness for group-3 and the NiTi alloy, group-3 (Co-Ni-Al + cr) showed more favourable results over the NiTi alloy. Where Co-Ni-Al-Cr alloy showed a high fatigue strength =733.33 than NiTi =400, which represents the highest stress that a material can withstand for a given number of cycles without breaking. Co-Ni-Ti alloy having chromium trace elements may replace NiTi in rotary root canal equipment based on wear, fatigue, corrosion resistance, and hardness.