CDA 955 (UNS C95500) Aluminum Bronze Pump Wear Ring: Material Properties, Applications & Selection Guide
CDA 955 (UNS C95500) Aluminum Bronze Pump Wear Ring: Material Properties, Applications & Selection Guide
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CDA 955 (UNS C95500) Aluminum Bronze Pump Wear Ring: Material Properties, Applications & Selection Guide
1. Overview: CDA 955 Aluminum Bronze for Pump Wear Rings
CDA 955 — also designated UNS C95500 — is a cast nickel aluminum bronze (NAB) in the copper-aluminum-iron-nickel family. It is selected for centrifugal pump wear rings where the operating duty combines corrosive media (seawater in particular), moderate to high mechanical loading, and sliding contact with steel or cast-iron impellers. The alloy can be supplied as-cast or in the TQ50 quench-hardened and temper-annealed condition for higher hardness.
This guide covers the material composition, mechanical and physical properties, wear ring functions and application positions, API 610 clearance and hardness pairing rules, comparison with alternative wear ring materials, and engineering selection guidance. Values are typical or minimum figures from public standards; verify all data against the governing specification before procurement.
2. Designation and Equivalent Standards
CDA 955 is the Copper Development Association number for UNS C95500, historically known as ASTM B148 alloy 9D. The table below lists common cross-references used in drawings, inquiries, and purchase orders.
| System | Designation | Notes |
|---|---|---|
| CDA / UNS (US) | CDA 955 / UNS C95500 | Primary designation for procurement |
| ASTM (US) | B148 (sand castings), B505 (continuous cast), B271 (centrifugal castings), B30 (ingots) | Formerly ASTM B148-9D |
| SAE (US) | J461 / J462, CA955 | Automotive / general engineering references |
| MIL (US) | MIL-B-16033 Class 4, QQ-C-390 | Defense procurement legacy references |
| EN (Europe) | EN 1982 CC333G | Compositional match: CuAl10Fe5Ni5 |
| DIN / ISO | CuAl10Fe5Ni5 (ISO 1338) | Common on European drawings |
| BS (UK) | BS 1400 AB2C | Legacy British designation |
Grade equivalents are intended for inquiry and drawing communication only; they do not replace verification of composition and properties against the governing standard.
3. Chemical Composition
| Element | Cu | Al | Fe | Ni (incl. Co) | Mn | Others, total |
|---|---|---|---|---|---|---|
| Limit | 78.0 min | 10.0 – 11.5 | 3.0 – 5.0 | 3.0 – 5.5 | 3.5 max | 0.50 max |
- Cu + sum of named elements: 99.5% min.
- Aluminum is the primary strengthening element; it forms an alpha-copper matrix strengthened by iron- and nickel-rich kappa-phase precipitates. Higher aluminum content raises strength but increases retained-beta and dealuminification sensitivity.
- Iron and nickel refine the grain structure, support wear resistance, and improve corrosion resistance and high-temperature strength retention compared with iron-only aluminum bronzes such as C95400.
- Supplier data sheets may list tighter manganese limits depending on product form; confirm against the specified standard and the batch mill certificate.
4. Mechanical and Physical Properties
4.1 Physical properties
| Property | Value | Notes |
|---|---|---|
| Density / specific gravity | 7.53 g/cm³ (0.272 lb/in³) | — |
| Melting range (solidus – liquidus) | 1038 – 1054 °C | — |
| Modulus of elasticity | 110 GPa (16,000 ksi) | Tension |
| Thermal conductivity | ≈ 42 W/(m·K) (24.2 Btu/ft·hr·°F) | At 20 °C |
| Coefficient of thermal expansion | ≈ 16.2 ×10⁻⁶ /°C (20–300 °C) | Used for clearance stack-up |
| Electrical conductivity | 8% IACS | Not intended for conductive service |
| Magnetic permeability | 1.32 (cast) / 1.2 (TQ50) | Weakly magnetic |
| Poisson’s ratio | 0.32 | — |
4.2 Mechanical properties by casting method and temper
Mechanical values depend on the casting process (sand, centrifugal, continuous, permanent mold) and the temper condition (as-cast M01/M02/M07 vs. TQ50). Purchase documents should state grade, standard, and temper explicitly.
| Condition / process | Tensile strength (MPa) | Yield strength (MPa) | Elongation (%) | Hardness (HB) | Notes |
|---|---|---|---|---|---|
| Sand cast, as-cast (M01) | 620 min (typ. 620–710) | 275–310 | 6–14 | 183–200 | Common starting point for wear rings |
| Centrifugal cast, as-cast (M02) | 620 min | 275 min | 6 min | 190 min | Preferred route for ring blanks |
| Continuous cast (M07) | 655 min | 290 min | 10 min | ≈ 190–208 | Bar/tube stock for machined rings |
| TQ50 quench-hardened + temper annealed | 758–760 min | 415–427 min | 5–8 | 200–230 | Selected for high-load, high-hardness duty |
| Compressive yield strength (as-cast, 10% set) | ≈ 825 | — | — | — | Reference for load-bearing faces |
| Fatigue strength (rotating beam, 10⁸ cycles) | ≈ 215 | — | — | — | Reference for cyclic loading |
| Machinability (C36000 = 100) | 50 (moderate) | Chip control required; not free-cutting | |||
TQ50: solution treatment ≈ 870–910 °C, water quench, then temper ≈ 620–660 °C for about 2 hours. Complex or thick-section parts may distort during quench; evaluate geometry before specifying heat treatment. For dimensionally sensitive machined rings, a low-temperature stress relief near 350 °C for at least 1 hour after rough machining is recommended.
5. Why C95500 Is Used for Pump Wear Rings
A pump wear ring (casing ring / impeller ring) is a replaceable component that establishes a controlled running clearance between the rotating impeller and the stationary casing. It limits internal recirculation, contributes to rotor stability (Lomakin effect), and protects the casing and impeller from wear. Material selection directly affects service life, efficiency retention, and maintenance cost.
| Characteristic | Behavior | Engineering relevance |
|---|---|---|
| Strength / hardness | High strength within cast copper alloys; HB 200–230 in TQ50 | Resists pressure loads and transient contact; reduces grooving |
| Seawater / corrosion resistance | Self-passivating Al₂O₃ + Cu₂O surface film | Suited to seawater pumps and marine pump services |
| Sliding wear resistance | Kappa-phase particles support load against steel/cast-iron counterfaces | Low wear rate in properly paired rubbing surfaces |
| Anti-galling behavior | Lower tendency to friction-weld than austenitic stainless steel | Safer under start/stop and transient contact; reduces seizure risk |
| Cavitation / erosion resistance | Good, above tin bronzes and general cast iron | Relevant to high-head and low-NPSH-margin pumps |
| High-temperature strength | Nickel-stabilized phases retain strength better than C95400 | Boiler feed and hot-process pump services |
| Machinability | 50/100, moderate; produces stringy chips | Requires tooling and chip-control strategy for precision bores |
| Castability | Low yield, high drossing, high solidification shrinkage | Centrifugal or continuous casting preferred for ring blanks |
| Cost | Higher than C95400 and tin bronzes | Economical only where the strength + corrosion + wear combination is required |
1) C95500 carries higher aluminum than C95800; under long-term continuous seawater immersion, dealuminification is a risk — verify C95800 for that service (ASTM B148 requires iron not to exceed nickel in C95800). 2) Do not pair C95500 directly with 316-type austenitic stainless steel without a hardness differential and clearance adjustment. 3) For sand-laden or highly abrasive slurries, bronze hardness is not sufficient; use hard-faced or tungsten-carbide solutions instead.
6. Application Positions in a Centrifugal Pump
| Pump service | Position | Recommended solution | Selection basis |
|---|---|---|---|
| Seawater pumps; marine ballast & cooling | Casing ring + impeller ring (front / rear) | C95500 as-cast or TQ50 | Seawater resistance plus dissimilar-metal rubbing pair; verify C95800 for continuous immersion |
| Fire-fighting pumps (engine driven) | Front and rear rings | C95500 as-cast (sand / centrifugal) | Corrosion resistance with high start-stop reliability |
| Power-plant boiler feed / condensate | Wear ring pairs per stage | C95500; allow clearance compensation for temperature | Nickel-stabilized high-temperature strength; add 0.125 mm for service above 260 °C |
| Chemical process pumps (non-oxidizing media) | Casing ring | C95500, or 316L / nickel-base alloys by media review | Resistance to non-oxidizing acids and process fluids |
| Submersible / sewage pumps | Wear plate (axial clearance face) | C95500 plate, or hardened 17-4PH | Cavitation and erosion resistance; hard-face for abrasive duty |
| Multi-stage centrifugal pumps | Ring pair at each stage | C95500 continuous-cast bar (small bore) / centrifugal casting (large bore) | Consistency and economy at volume |
| High-abrasion slurry pumps | Wear rings | Not bronze — tungsten carbide / hardened white cast iron | Bronze hardness is insufficient for particle erosion |
7. Clearance and Hardness Pairing Rules
7.1 Hardness differential (API 610)
The Brinell hardness difference between mating wear ring surfaces should be at least 50 HB, unless both surfaces are at least 400 HB. C95500 (183–230 HB) satisfies this rule against hardened steel or 17-4PH (300 HB and above). Against 316 austenitic stainless steel (149–200 HB) the differential is insufficient and 316 has a high galling tendency — use hardened 410-type steel as the counterface, or add 0.005 in (0.125 mm) to the nominal diametral clearance.
7.2 Minimum diametral clearance (API 610 Table 6)
| Rotating member diameter (mm) | Min. diametral clearance (mm) | Rotating member diameter (mm) | Min. diametral clearance (mm) |
|---|---|---|---|
| < 50 | 0.25 | 275 – 299.99 | 0.58 |
| 50 – 64.99 | 0.28 | 300 – 324.99 | 0.60 |
| 65 – 79.99 | 0.30 | 325 – 349.99 | 0.63 |
| 80 – 89.99 | 0.33 | 350 – 374.99 | 0.65 |
| 90 – 99.99 | 0.35 | 375 – 399.99 | 0.68 |
| 100 – 114.99 | 0.38 | 400 – 424.99 | 0.70 |
| 115 – 124.99 | 0.40 | 425 – 449.99 | 0.73 |
| 125 – 149.99 | 0.43 | 450 – 474.99 | 0.75 |
| 150 – 174.99 | 0.45 | 475 – 499.99 | 0.78 |
| 175 – 199.99 | 0.48 | 500 – 524.99 | 0.80 |
| 200 – 224.99 | 0.50 | 525 – 549.99 | 0.83 |
| 225 – 249.99 | 0.53 | 550 – 574.99 | 0.85 |
| 250 – 274.99 | 0.55 | 600 – 624.99 | 0.90 |
- Correction: add 0.125 mm (0.005 in) for galling-prone material combinations (e.g., 316 against 316) or for all materials in service above 260 °C (500 °F).
- Simple rule of thumb when OEM data is unavailable: below 5 in diameter, 0.010 in + 0.002 in per inch; 5–10 in, 0.015 in + 0.001 in per inch; add 0.005 in for galling-prone materials.
- Replacement criterion: replace rings when clearance reaches roughly twice the original value (some manufacturers use 140%); a 0.5 mm increase in clearance can reduce pump efficiency by about 3–5%.
8. Wear Ring Material Comparison
| Material | Hardness (HB) | Corrosion | Wear | Anti-galling | Typical service | Limitations |
|---|---|---|---|---|---|---|
| C95500 (this guide) | 183–230 | High (seawater, non-oxidizing) | High (load type) | Good (vs. steel) | Seawater, boiler feed, chemical, marine pumps | Higher cost; check dealuminification for continuous seawater; not for abrasive slurry |
| C95400 | ≈ 170–200 | High | High | Good | General high-strength rings, cost-effective | Slightly lower high-temperature and corrosion performance |
| C95800 | ≈ 160–200 | High (stronger dealuminification resistance) | Good–high | Good | Long-term seawater immersion (propeller class) | Lower strength than C95500; less heat-treatable |
| C93200 / SAE 660 tin bronze | 60–80 | Good | Moderate | Good | Clean water, boundary lubrication, free machining | Low strength; faster wear under heavy load |
| 316 stainless steel | 149–200 | High (general chloride) | Moderate | Low (galls) | Corrosive chemical media | Needs +0.005 in clearance; avoid self-pairing |
| 410-type hardened steel / 17-4PH | 200–400+ | Good | High | Moderate | Counterface for bronze rings; heavy duty | Corrosion-sensitive; may need coating |
| Hardened white cast iron | 450–650 | Moderate | High (abrasive) | — | Abrasive slurry, wastewater | Brittle; limited impact tolerance |
| Tungsten carbide (WC-Co) / HVOF coating | 1200–1400 HV | Good | Very high | — | Severe abrasion (sand, ore slurry) | High cost; difficult machining |
| PTFE / carbon graphite / PEEK | — | High | Moderate | Good (self-lubricating) | Chemical, food, potable water (non-metallic) | Limited temperature and pressure |
9. Selection Guidance
- Media check: high particle loading or abrasive slurry → tungsten carbide / hardened white cast iron hard-facing, not bronze.
- Corrosion check: long-term continuous seawater immersion → verify C95800 (dealuminification resistance); otherwise C95500 is suitable.
- Load and temperature check: high load, high speed, or high temperature → specify C95500 TQ50 and apply the API 610 temperature correction to clearances.
- Cost check: clean water, low load → C95400 or C93200 may meet the requirement at lower cost.
- Pairing verification: confirm at least 50 HB differential (or both faces ≥ 400 HB); avoid 316-to-bronze pairing without clearance correction.
10. Manufacturing and Quality Control Notes
- Blank production: centrifugal casting for dense, sound ring blanks; continuous-cast bar for small-volume machined rings; sand casting for large sizes with strict feeding design (high shrinkage, drossing tendency).
- Heat treatment: evaluate distortion risk before specifying TQ50; low-temperature stress relief after rough machining.
- Machining: machinability rating 50/100; stringy chips require chip-breaker tooling and controlled parameters; avoid tearing on bored surfaces.
- Precision: bores, concentricity (TIR), and surface finish (typically Ra 1.6–3.2 µm on running faces) control the running clearance; set diametral clearance per API 610 Table 6.
- Fixing: press fit with locking pins / set screws / tack welding; provide removal steps.
- Inspection: chemical composition, hardness (HB), dimensional checks, and material certificates (e.g., EN 10204 3.1).
- Documentation: state grade + standard (ASTM B148/B505) + temper (M01/M07/TQ50) + casting method; avoid the generic term “nickel aluminum bronze” in specifications.
11. Frequently Asked Questions
Is C95500 a suitable material for seawater pump wear rings?
Yes. C95500 offers high corrosion resistance in seawater with high strength and good sliding-wear performance, and it forms a non-galling rubbing pair with steel or cast-iron impellers. For components in continuous long-term seawater immersion, C95800 is commonly verified instead because of its stronger dealuminification resistance.
What is the difference between C95500 and C95400 for wear rings?
C95500 adds nickel (3.0–5.5%), which improves corrosion resistance, toughness, and high-temperature strength retention. C95400 is an iron-bearing aluminum bronze without the nickel addition; it is lower cost and is often sufficient for general water and moderate-duty services.
What clearance should a C95500 wear ring have?
Use the minimum diametral clearances of API 610 Table 6 based on the rotating member diameter (e.g., 0.25 mm below 50 mm, 0.55 mm at 250–274.99 mm). Add 0.125 mm (0.005 in) for galling-prone material combinations or service above 260 °C. Where OEM data exists, follow the OEM recommendation.
Can C95500 wear rings be paired with stainless steel impellers?
Yes, but verify the hardness differential (at least 50 HB unless both faces are ≥ 400 HB). Against 316 austenitic stainless steel the differential may be insufficient and 316 is prone to galling; hardened 410-type steel or 17-4PH counterfaces are commonly used, or the nominal clearance is increased by 0.005 in.
When should C95500 not be used for wear rings?
For high-abrasion slurry service (particle erosion), for strong oxidizing chemicals outside the alloy’s corrosion range, and where continuous seawater immersion with dealuminification risk applies — in those cases, tungsten carbide / hard-facing, stainless or nickel-base alloys, or C95800 should be evaluated.
Version Rev.1 EN · 2026-08-27 · Technical SEO guide derived from deep-research draft Rev.1 (Chinese)
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