Composition of classic tin-base Babbitt bearing metal Which of the following compositions corresponds to a standard tin-base Babbitt alloy used for hydrodynamic bearing linings?

Introduction / Context:
Babbitt metals are soft bearing alloys designed to operate under hydrodynamic lubrication with excellent embeddability and conformability. Their microstructure combines a soft matrix with hard intermetallics for wear resistance, making composition recognition useful in maintenance and materials selection.

Given Data / Assumptions:

• Tin-base Babbitts use Sn as the matrix with additions of Sb and Cu to form hard phases.
• Typical premium compositions cluster around Sn ~88–90%, Sb ~7–8%, Cu ~3–4%.
• Lead-base Babbitts form a different family with higher lead content.

Concept / Approach:
A classic tin-base Babbitt contains approximately 88% Sn, 8% Sb, and 4% Cu. Antimony and copper form hard compounds dispersed in the tin matrix, providing load capacity and wear resistance while the soft matrix accommodates misalignment and debris. This balance underpins the success of Babbitts in turbines, compressors, and pumps.

Step-by-Step Solution:
Identify the tin-base range: high Sn (≈88–90%) with modest Sb and Cu.Compare options: only option (c) matches the canonical tin-base composition.Exclude clearly incorrect ratios (e.g., 50–50 Sn–Sb or high Cu content).Therefore, select 88% tin, 4% copper and 8% antimony.

Verification / Alternative check:
Standards and handbooks list multiple grades (e.g., ASTM) with compositions close to 88Sn–8Sb–4Cu for high-performance tin-base Babbitts.

Why Other Options Are Wrong:
(a) lacks copper and is unrealistically high in Sb; (b) has excessive copper; (d) is atypical and lacks sufficient Sb; (e) describes a lead-base alloy, not a tin-base Babbitt.

Common Pitfalls:
Confusing tin-base and lead-base Babbitts; they serve different temperature and load regimes.

Final Answer:
88% tin, 4% copper and 8% antimony