https://jeekrapid.com/blog/surface-hardening-a-key-technique-to-make-metal-parts-more-durable/
Surface Hardening: A Key Technique to Make Metal Parts More Durable
Jul 29, 2025 - Surface hardening includes physical or chemical treatments that harden only the outer layer of metal parts. When applied to steel, these techniques are called...
a key techniquesurface hardeningto makemetal parts