Bearing alloys — classification of Babbitt metal Babbitt metal, widely used as a bearing lining material for hydrodynamic bearings, is typically classified as which base-alloy type?

Introduction / Context:
Babbitt metals are soft bearing alloys long used to line plain (journal) bearings. Their ability to embed debris, conform to slight misalignments, and resist seizure makes them essential in many rotating machines. Understanding their base alloy families aids selection for load and temperature conditions.

Given Data / Assumptions:

• Classical Babbitt metals come in two principal families: tin-base and lead-base.
• Applications emphasize hydrodynamic lubrication with adequate oil film formation.
• Performance depends on matrix softness with hard intermetallics dispersed for wear resistance.

Concept / Approach:
Tin-base Babbitts (e.g., Sn–Sb–Cu) are considered the archetypal Babbitts with superior fatigue resistance and corrosion performance compared to many lead-base versions. Lead-base Babbitts are less costly and used for lower loads and temperatures. When the generic term “Babbitt metal” is used in basic materials questions, it usually refers to tin-base Babbitt unless specified otherwise.

Step-by-Step Solution:
Identify family: tin-base versus lead-base Babbitts.Relate to performance: tin-base exhibits better high-speed, moderate-load capability.Match with general definition: “Babbitt metal” historically denotes tin-base compositions.Therefore select “tin-base alloy”.

Verification / Alternative check:
Standards and handbooks list classic compositions such as Sn–Sb–Cu systems for premium Babbitts used in turbines and compressors.

Why Other Options Are Wrong:
Copper-base and aluminium-base bearings exist (e.g., bronzes, Al–Sn alloys) but are not Babbitts; cadmium-base is not a standard bearing lining alloy; lead-base Babbitt exists but is a different family and not the canonical answer when “Babbitt metal” is asked generically.

Common Pitfalls:
Assuming all soft bearing metals are “Babbitt”; many non-Babbitt bearings (bronze, polymer) serve different regimes and properties.

Final Answer:
tin-base alloy