Stainless Alloy Steel C50TF84 (GE) Bars, C50TF84 (GE) Rods

Product Description

It looks like your query cut off slightly, but if you are currently sourcing, machining, or auditing stock for C50TF84 bars and rods, here is the critical technical and processing data you need to ensure compliance with this specific General Electric Aviation standard.

Technical Baseline: AMS 6278 / CBS-50 NiLâ„¢

While classified broadly on inventory sheets as a stainless or high-alloy steel, C50TF84 is GE’s internal specification for CBS-50 NiL (UNS K91231). It is a premium, double-vacuum melted (VIM-VAR), low-carbon carburizing steel engineered specifically for aircraft gas turbine engine components.

Chemical Composition (Weight %)

The alloy achieves its high-temperature strength and extreme core toughness through a precise balance of secondary hardening elements:

• Carbon (C): 0.11% – 0.15% (Kept low to ensure a ductile, fracture-resistant core)

• Chromium (Cr): 4.00% – 4.25% (Provides hardenability and basic oxidation resistance)

• Nickel (Ni): 3.20% – 3.60% (Maximizes impact strength and prevents brittle fractures)

• Molybdenum (Mo): 4.00% – 4.50% (Prevents structural softening at high operating temperatures)

• Vanadium (V): 1.13% – 1.33% (Forms ultra-hard, wear-resistant grain-refining carbides)

Machining & Processing Requirements

If you are preparing to process or machine C50TF84 round bars or rods, keep the following metallurgical traits in mind:

1. Delivery Condition

Bars and rods are typically supplied in the annealed and cold-finished or hot-rolled turn-ground condition, showing a typical hardness of ≤ 25 HRC (around 255 HBW). In this state, the microstructure is optimized for standard carbide tooling, though it exhibits high work-hardening tendencies similar to tool steels.

2. Carburizing and Heat Treatment

Because the base carbon content is low ($0.13\%$ nominal), parts machined from these rods must undergo a specialized gas or vacuum carburizing cycle to diffuse carbon into the surface layer.

• The Goal: Achieve a high-carbon surface case ($0.80\%$ to $1.00\%\text{ C}$) while leaving the low-carbon nickel core untouched.

• Final Hardness: After a subsequent oil quench and multiple tempering cycles (typically around $1000^\circ\text{F}$ / $538^\circ\text{C}$ to utilize the secondary hardening effect of Mo and V), the surface case reaches 60–64 HRC for wear resistance, while the core remains a highly fracture-tough 35–42 HRC.

3. Thermal Stability

Unlike standard AISI 8620 or 9310 carburizing steels which soften dramatically above $300^\circ\text{F}$ ($149^\circ\text{C}$), parts machined from C50TF84 maintain their case hardness and rolling-contact fatigue life at continuous service temperatures up to $600^\circ\text{F}$ ($316^\circ\text{C}$).

Critical Manufacturing Standards

When executing a purchase order or generating a quality plan for this material, it is common to cross-reference the following overlapping specifications: