Investigation of Wear Behaviour for NiTi Alloys with Yttrium and Tantalum Additions

Abstract

A study of the effects of added Yttrium and Tantalum on the wear behaviours of NiTi shape memory alloys was completed to examine the effects of compacting pressure levels between 400 and 650 MPa and to investigate wear parameters such as load, sliding distance, and time to determine the wear rate for the prepared alloys. Several alloys were prepared using a powder metallurgical technique; the powder mixture had a basic chemical composition of 55% Nickel and 45% Titanium, and alloying elements of Yttrium and Tantalum were then added at weight percentages 1, 2, and 3 wt% of each element (at the expense of nickel) before the powders were mixed then compacted under a range of compacting pressures (400, 500, 600, and 650 MPa) to form cylindrical samples, Sintering was completed in two steps. The first step was done at a temperature of 500 °C for two hours, while the second step was done at 850 °C for six hours, both under vacuum conditions (6.7 E −02 Pa). The generated specimens were then left to cool. The wear behavior was then studied using pin-on-disk tests at variable loads and times (2, 5, 10, and 15 N and 5, 10, 15, and 20 min, respectively). XRD testing, apparent density and porosity, hardness, and surface roughness tests were also completed in this study. From the results, it is clear that the wear volume loss decreases with the addition of Tantalum by 0.52% with 3% Tantalum addition at 650 MPa compacting stress for a 15 N load; it also decreases by 0.48% with 2% Yttrium addition at 650 MPa for a 10 N load. The wear volume loss further decreases as the compacting stresses increase. In addition, the wear rate increased as the load and time increased for all tested specimens.