Indentation Creep Behaviors of SnSb8Cu4 Babbitt Alloy with Zn and Cu Addition

Abstract

In the present study, the effects of copper and zinc addition on the microstructure and indentation creep behaviors of SnSb8Cu4 Babbitt alloy were systematically investigated. An indentation creep testing device with a flat tip indenter was used to characterize the creep behaviors of the Babbitt alloys at ∼100°C with different loads. By increasing the copper content from 4 wt% to 8 wt%, coarser and shorter Cu₆Sn₅ dendrites with larger volume fraction were observed. The corresponding Brinell hardness increased from 21.9 to 28.1 at room temperature. However, the improvement in creep resistance was not obvious. After adding 0.72 wt% zinc, large number of small-sized SnSb particles precipitated along the grain boundaries of tin matrix. The total volume fraction of intermetallics, i.e., Cu₆Sn₅ and SnSb particles, increased from 15.1% to 20.9%. Although, the increment of Brinell hardness was not remarkable at room temperature, dramatic improvement in creep resistance was observed. The addition of zinc caused the decrement of the solid solubility of Sb in tin matrix, while more network-like SnSb particles precipitating in tin matrix were found, giving rise to the pinning effect against grain boundary sliding during creep deformation. However, increment of copper content showed no obvious effect on the solid solubility of Sb in tin matrix. Meanwhile, an exponential relationship between indentation creep rate and indentation stress at the steady creep stage was found. Based on the measured data, the indentation stress exponent of SnSb8Cu4, SnSb8Cu8 and SnSb8Cu4Zn was deduced to be 2.949, 2.865 and 2.743, respectively.

Small amount of Zn addition leads to large numbers of SnSb particles precipitating along the grain boundaries of SnSb8Cu4 matrix, showing great pinning effect against grain boundary slip during creep deformation and thus resulting in a dramatic improvement in creep resistance.