Synthesis of As-sintered 60NiTi Parts with a High Open Porosity Level

Abstract

60NiTi, despite exhibiting attractive chemical and mechanical properties desirable for biomedical applications, has not yet been processed to a porous structure suitable for general bone replacement applications. In this research, elemental Ni and Ti powders were used to process and manufacture 60NiTi parts by employing conventional press-and-sinter method. Blended Ni and Ti powders provided the possibility of liquid formation in the samples during sintering which leaded to an increase in porosity. Different processing parameters such as pressing pressure, sintering temperature, heating rate and sintering holding time were investigated in a systematic way to obtain 60NiTi parts with approximately 30 Vol.% open porosity. Further, the effects of these processing parameters on the microstructure, phase structure and dimensional stability of the as-sintered parts were investigated. Porous parts with satisfactory dimensional stability were obtained in all cases. It was found that applying lower compaction pressure, final sintering temperatures of above 942°C, faster heating rates and shorter sintering time were beneficial in terms of obtaining parts with more open porosities. Samples sintered at a final temperature of 1050°C did not contain any elemental Ni or Ti material and were ready to be solutionized to obtain hard biocompatible 60NiTi parts.

Fabrication of Ni-Rich 58NiTi and 60NiTi from Elementally Blended Ni and Ti Powders by a Laser Powder Bed Fusion Technique: Their Printing, Homogenization and Densification

“…In essence, the reason for choosing this HIP temperature was that it is above 942 °C where a eutectic liquid ( Figure 1 ) is estimated to be generated amongst β-Ti phase and Ti 2 Ni intermetallic, formed around β-Ti in the as-printed samples ( Figure 6 ) [ 40 , 41 , 42 , 43 ]. It is thought that the generation of this liquid will enhance the homogenization process as, under such conditions, the reaction rate amongst different phases is expected to be increased [ 36 , 44 ].…”

“…Note that these tests were performed on the cross-section of the ground, polished, and etched samples and the images were obtained in parallel to the building direction (BD) of parts. The receipt for the preparation of the Ni-rich NiTi parts for microstructural studies is discussed and explained in [ 40 , 41 , 42 , 44 ]…”

“…Note that these tests were performed on the cross-section of the ground, polished, and etched samples and the images were obtained in parallel to the building direction (BD) of parts. The receipt for the preparation of the Ni-rich NiTi parts for microstructural studies is discussed and explained in [40][41][42]44] A Rockwell hardness tester, using a conical diamond indenter applying 150 Kg load, was used to measure the Rockwell C hardness (HRC) of the processed parts. These tests were performed 10 times and the average results are reported.…”

Toz metalurjisi ile Üretilen NiTi Alaşımına Al'un Etkisi

“…Katıhal difüzyonuna bağlı olarak NiTi2 faz miktarı azalırken Ni3Ti ve NiTi fazlarının oluşumu gerçekleşir. NiTi ve Ni3Ti fazlarının oluşmasında önemli rol oynayan katı hal düfizyon hızı ısıtma hızı ve hammaddelerin yoğunluğuna bağlıdır [31][32][33].…”