FD-0205 Fatigue and Strength Data

The Question Behind This Page

An engineer recently asked on a public forum, in almost these words: "I am trying to find surface-fatigue strength (AGMA) for powder metal gears, particularly FD-0205-95HT." The thread exists because the question is genuinely hard to answer from a search engine. The strength data for FD-0205 lives in MPIF Standard 35 (and its ASTM B783 equivalent), which are paid standards; the numbers are condition- and density-dependent; and the fatigue values that gear designers actually need — allowable contact stress numbers in AGMA format — sit in a second paid standard most buyers have never heard of.

This page puts in one place what is publicly verifiable about FD-0205: what the alloy is, how the grade code works, what the heat-treated strength data says, and how to get from "FD-0205-95HT" to a usable gear-fatigue number. For the broader discipline of reading PM fatigue data — density labels, condition labels, evidence levels — read our PM fatigue design data guide first; this page is the single-grade deep dive.

What FD-0205 Is

FD-0205 is a diffusion-alloyed steel in the MPIF FD family. In diffusion alloying, alloying elements are bonded onto an iron powder surface at high temperature before compaction, which gives far more homogeneous chemistry through the part than a simple premix — and chemistry homogeneity is exactly what a heat-treated fatigue part needs.

The composition matches well-known commercial diffusion-alloyed powders of the Distaloy AE type, which is why FD-0205 parts behave consistently across powder suppliers. The grade is a standard choice for heat-treated, fatigue-loaded parts — gears, sprockets, latches, and high-strength structural components — where its nickel-copper-molybdenum combination hardens deeply and predictably in quench-and-temper. Density is specified by the buyer within the family's practical press-and-sinter window of roughly 6.7–7.4 g/cm³, and nearly every property below moves with that density choice.

Reading the Grade Code: What "-95HT" Actually Means

The suffix is not decoration — it is the minimum-strength designation language of MPIF Standard 35 / ASTM B783, and misreading it is the most common specification error with FD-0205.

So FD-0205-95HT promises a minimum tensile strength of 95 ksi (≈655 MPa) in the heat-treated condition — and, importantly, in heat-treated PM steels the yield strength is approximately equal to the tensile strength, with elongation typically under 1%. If your drawing says "-95HT" but your supplier quotes as-sintered properties, the part you receive will not be the part the code promises. Our ASTM B783 grade-system page works through the suffix rules grade by grade.

Heat-Treated Strength Data

Published FD-0205 heat-treated grades run from -95HT through -160HT, with minimum tensile strengths set by the suffix and achieved through density and heat treatment together:

Two data points behind the table, from the ASM Handbook's reproduction of MPIF 35 data: a typical FD-0205-95HT material tests around 720 MPa (105 ksi) tensile with under 1% elongation, at an apparent hardness near 28 HRC with a converted matrix microhardness around 55 HRC — the gap between those two hardness readings being the porosity effect itself. The exact density-to-grade mapping changes between standard editions; verify cells that matter against the current edition of MPIF Standard 35 before locking a drawing, which is the same advice we give for every grade on this site.

Surface Fatigue and the AGMA Question

The forum question was about surface fatigue — gear tooth pitting — and that is a different dataset from tensile strength. The document that governs it is AGMA 6006, "Specifications for Powder Metallurgy Gears," a joint AGMA/MPIF standard that exists precisely because PM gear allowables cannot be copied from wrought-steel tables: porosity, density gradients, and surface condition change the contact-fatigue behavior enough that a PM-specific standard was needed.

What this means practically:

• Do not scale wrought AGMA allowable stress numbers down by a rule of thumb. The PM-specific numbers exist; use them or use part-specific test data.
• AGMA 6006-based allowables are the right ask when a gear drawing references AGMA ratings. Suppliers who serve gear OEMs can produce allowable stress numbers in that framework or explain exactly which basis they use instead.
• Surface densification changes the answer. Rolling or re-pressing the tooth flanks after sintering densifies the surface layer — the exact layer where contact fatigue initiates — and published rolling-contact-fatigue work on densified PM steels shows substantial improvement over as-sintered surfaces. For RCF-critical gears, "is the flank densified, and to what depth?" is a more productive question than "what is the fatigue strength?"
• Root bending and tooth accuracy interact with material data. Our PM gears overview covers tooth design and accuracy classes, and the fatigue design data guide covers the evidence ladder — handbook data, specimen data, part-level testing — that a fatigue-critical program should climb.

What Moves FD-0205 Fatigue Performance

In rough order of leverage, for a fixed grade:

1. Density. Fatigue limits in sintered steel rise steeply with density through the 6.8–7.2 g/cm³ window; it is the single strongest lever, ahead of alloy choice.
2. Heat-treatment condition. The -HT suffix is earned by quench-and-temper; tempering temperature trades hardness against toughness, so the temper matters as much as the quench.
3. Surface condition. Shot peening and surface densification close or compress surface-connected pores — the initiation sites for both bending and contact fatigue.
4. Geometry discipline. Fillets, passage exits, and notch features concentrate stress more severely in porous steel than in wrought; good PM gear geometry already accounts for this.

None of these have universal coefficients — typical values vary by density and sintering conditions — which is why a responsible supplier answers fatigue questions with a material and density proposal plus an evidence level, not a single number pulled from a table.

Specifying FD-0205 on a Drawing

A complete FD-0205 callout answers five questions before quoting starts:

• Grade and suffix — e.g., FD-0205-95HT, not bare "FD-0205".
• Minimum density — stated in g/cm³, and whether it applies to the whole part or a critical zone.
• Heat-treat condition — quench-and-temper with tempering range, plus any case requirements.
• Surface densification — required or not on tooth flanks, and to what effective depth.
• Evidence level — handbook data acceptable, or specimen/part-level fatigue verification required.

Bring the duty cycle with the drawing when you request a quote — a torque-speed-load history lets engineering propose the density tier and heat-treat window honestly rather than quoting the lowest-cost compliant grade. If you are still comparing processes at the concept stage, the PM cost calculator frames the tooling-amortization arithmetic, and our about page introduces the factory behind the data.