Alloy Steel PWA 36140 (Pratt & Whitney) Bars / PWA 36140 Rods / PWA 36140 Rings

Product Description

PWA 36140 is a high-performance aerospace material specification from Pratt & Whitney, primarily identifying a carburizing bearing and gear steel known commercially as M50 NiL (or CBS-50 NiL).

Unlike standard M50 through-hardened steel, PWA 36140 is designed to be carburized, providing a hard, wear-resistant surface (case) while maintaining a high-toughness core. This makes it ideal for critical aircraft engine components that face both high-stress rolling contact and potential impact.

1. Core Material Equivalents

PWA 36140 is effectively the Pratt & Whitney equivalent of several other high-end aerospace and industry standards:

• AMS Specification: AMS 6278

• UNS Number: UNS K91231

• Commercial Name: M50 NiL / CBS-50 NiL

• Other OEM Equivalents: * GE: B50TF347 (formerly B50TF211)

  • Rolls Royce: MSRR 6113

  • SKF: MS-229

2. Chemical Composition (Nominal %)

The "NiL" stands for Nickel-Low Carbon, which distinguishes it from standard M50. The low carbon content allows for superior fracture toughness in the core after carburizing.

3. Key Technical Properties

• Melt Type: Typically produced via VIM-VAR (Vacuum Induction Melting followed by Vacuum Arc Remelting) for extreme cleanliness and fatigue resistance.

• Service Temperature: Maintains strength and stability up to approximately 316C (600F).

• Core Toughness: Unlike standard M50, which can be brittle, PWA 36140 has high fracture toughness ($>40 \text{ ksi}\sqrt{\text{in}}$), making it resistant to catastrophic failure if a crack initiates.

• Case Hardness: When carburized and heat treated, the surface achieves a hardness of 60-64 HRC, comparable to tool steels.

4. Available Product Forms

As an aerospace-grade material, it is strictly controlled and supplied in the following forms for further machining or forging:

• Round Bars / Rods: Used for machining engine bearings, shafts, and fasteners.

• Rings: Often supplied as forged rings for bearing races and gear blanks.

• Billets: For large-scale forging operations.

5. Applications

• Main Shaft Bearings: The primary application in jet engines.

• High-Performance Gears: Where high surface fatigue life and core shock resistance are required.

• Aerospace Fasteners: Critical bolts subjected to high temperatures and loads.