In the field of materials science, martensitic stainless steel occupies a unique position due to its heat-treatable strengthening property, with 431 steel (Chinese grade: 1Cr17Ni2) being a typical representative. Its performance stems from precise alloy design:

💠 Carbon content (≤0.20%), as interstitial atoms, is the core of martensitic transformation. Quenching after austenitization forms a supersaturated body-centered tetragonal structure (martensite), providing the material with initial high strength and hardness.

💠 Chromium content (15.0-17.0%) ensures the formation of a stable and dense passive film (Cr₂O₃) on the metal surface. This is the fundamental reason for the material’s resistance to corrosion from the atmosphere, water vapor and various media, endowing it with the “stainless” characteristic.

💠 Appropriate nickel content (1.25-2.50%) is not used to stabilize austenite. Its main role is to improve the hardenability of the steel and effectively enhance the toughness and ductile-brittle transition temperature of the martensitic steel.

This strengthening mechanism, combining precipitation strengthening and solid solution strengthening through heat treatment, enables 431 stainless steel to balance moderate corrosion resistance with strength and hardness far exceeding those of austenitic stainless steel (e.g., 304). Thus, it is widely used in applications requiring rigorous mechanical properties, such as aero-engine structural components, high-strength drive shafts, pump and valve parts, and corrosion-resistant fasteners—achieving an excellent engineering balance between material strength, hardness and corrosion resistance.

✨ Steps for Preparing Metallographic Samples of 431 Martensitic Stainless Steel

1️⃣ Rough grinding: P400 sandpaper

2️⃣ Fine grinding: POS + 9μm polycrystalline diamond

3️⃣ Rough polishing: YS-JP + 3μm polycrystalline diamond

4️⃣ Fine polishing: ZN-JP + 50nm silica

5️⃣ Etching: Ferric chloride-hydrochloric acid aqueous solution #SteelMicrostructure #MaterialScience #Metallography #SteelSamples #MicrostructureAnalysis #SteelPrep #MaterialTechnician #SamplePreparation #Microscopy #MetallurgicalTesting #SteelAlloys #SteelPolishing #MicrostructureTesting #MetallographyLab #MaterialAnalysis #SteelQuality #MicroscopicView #MetallurgicalEngineering #LabTechLife #MaterialsTesting #StructuralAnalysis #metallurgymonday #crosssection #coldmounting