Abstract
ABSTRACT
The effects of B content on the properties of Ni-Cr-Mo-B P/M material with Ni-22mass%Cr-Xmass%Mo-Ymass%B compositions ((X,Y) = (23,1.0), (26,1.6), (30,2.1), (33,2.6)) were investigated. Raw material powders were produced by gas atomization, followed by sieving under 500 μm in the particle size. And then, these powders were consolidated by HIP. HIP process was carried out at 1423 K in the temperature, at 147 MPa in the pressure and for 5 h in the holding time. All specimens consisted of γNi matrix with the composition of almost Ni-23%Cr-16%Mo and tetragonal M3B2 type complex boride.
Rockwell hardness increased and Charpy impact value decreased with increasing B content. The variation in bending strength as a function of B content showed the local maximum at 1.6%B. It is considered that this variation is caused by the both effects of hardening and embrittling with increasing B content. Wear resistance by Ohgoshi-type abrasion test improved with increasing B content. Compared with Co-C-Cr-W P/M material, even if Rockwell hardness of Ni-Cr-Mo-B is equivalent to that of Co-C-Cr-W, Ni-Cr-Mo-B shows higher wear resistance than Co-C-Cr-W. As a result of immersion test in HF aqueous solution, all Ni-Cr-Mo-B P/M materials showed higher corrosion resistance than C-276 alloy.
