Effect of Laser Surface Treatment on Transition Temperature of Ni/Ti SMAS

Abstract

It is well established that SMAs have a great important as: engineering and biomaterial applications, because of unique properties that had as well as, good biocompatibility. however, duo to its possible corrosion in physiological solution, dissolution of toxic Ni might be happening. Several studies have been carried out to improve the stability of the passive protective film of Tio2 and prevent the Ni ion relies out of NiTi. Surface treatment is one of these methods or techniques such as, ion implantation, plasma electro polishing, passivation, ultra-sonic treatment and laser treatment, most of these treatments are effects on transition temperatures (As,Af,Ms,Mf). Change of these temps. will affected the normal use especially in human body, so keeping these temps. within the range of the human body is of main requirements to Evaluation the efficiency of any treatment. In this study (55 wt% Ni, 45 wt % Ti) SMAs has been prepared by (PM), compacted at 850 MPa and sintered. Laser pulses deposition technique at (1064, 532) nm at different energy (2, 2.3, 2.7) J. At power (200) wat in constant duration time (2 ns) has been used to modify surface by continuous stricks (side by side) to study mechanical, corrosion properties and how laser pulses effects on transition temp. All results confirmed that there is a positive effect on properties, % improving in hardness with respect to reference sample are (145, 132.8, 123.8) and (180.9, 169.5, 152.3) at 1064, 532 wave length respectively. Improvement in Ni relies are equal to (52, 38) % with respect to reference sample. On the other hand, there are slight positive change on transition martensitic transformation, thermal hysteries ( As−Ms) there are reduction in degress from 50°C (untreated sample) to (36.9, 33.6)°C, while for martensitic transformation ( Af−Mf) the degress are decrease from (65)°C for untreated sample to (57.5, 51.7)°C wave length respectively.