Interdiffusion and the vacancy wind effect in Ni–Pt and Co–Pt systems

Abstract

In this study, bulk and multifoil diffusion couple experiments were conducted to examine the interdiffusion process in Ni-Pt and Co-Pt binary alloy systems. Inter-, intrinsic-, and tracer-diffusion coefficients at different temperatures, and as a function of the composition, were estimated by using the experimental data. Results show that in both the alloy systems, Pt is the slower diffusing species, and hence the interdiffusion process is controlled by either Ni or Co. The thermodynamic driving force makes the intrinsic diffusion coefficients of Co and Ni higher in the range of 30-70 at.%. The low activation energy for Co and Ni impurity diffusion in Pt compared with Pt in Ni and Co indicates that the size of the atoms plays an important role. The vacancy wind effects on the diffusion process are examined in detail, and it was demonstrated that its contribution falls within the experimental scatter and hence can be neglected.

Diffusion pattern in MSi2and M5Si3silicides in group VB (M = V, Nb, Ta) and VIB (M = Mo, W) refractory metal-silicon systems

“…Thus, we come to the conclusion that by ignoring the correlation effects (i.e. the vacancy wind factor) one overestimates somehow the ratio We have already shown in few cases that by ignoring the vacancy wind effect we do not introduce a significant error in the calculated diffusion parameter data compared to the experimental uncertainties one should expect [55,56].…”

Interdiffusion and solid solution strengthening in Ni–Co–Pt and Ni–Co–Fe ternary systems

“…Similar behaviour is found when Ni(xPt) alloys are coupled with Co, which indicates that Ni must have higher diffusion rate than Pt. In fact in binary Ni-Pt and Co-Pt [7] systems also Pt had lower diffusion rate compared to other elements. However, no significant variation in the interdiffusion zone thickness was found when NiCo (Ni25Co, Ni50Co and Ni75Co) alloys are coupled with Pt.…”

“…In earlier studies, we have examined interdiffusion in the Ni-Pt, Co-Pt [7] and Ni-Co [20] binary systems wherein the temperature range for annealing was selected such that the interdiffusion zone develops in complete solid solution. Results of this study indicate that Ni and Co are the faster diffusing species in the Ni-Pt and the Ni-Co systems, respectively, over the whole composition range.…”

“…Further, the driving force for diffusion in a particular system for both the diffusing species at a particular composition is the same [7].…”

“…Because of the presence of many elements, it is not easy to understand the effect of Pt on diffusion of other elements. Recently, we have conducted a comprehensive interdiffusion study in Ni-Pt and Co-Pt binary systems [7]. It should be noted that Co is an important alloying addition in the Ni-based superalloys and in certain applications Co-based superalloys are preferred.…”