Alleima® (formerly Sandvik Materials Technology) 14C28N is a martensitic stainless chromium steel with a chemistry optimized for high quality professional knife applications. The chemical composition provides a unique combination of properties including: Excellent edge performance Very high hardness Good corrosion resistance Alleima® (formerly Sandvik Materials Technology)14C28N is mainly recommended for knife applications which put very high demands on edge sharpness, edge stability and corrosion resistance. Examples are pocket knives, chefs knives, hunting knives and fishing knives. Chemical composition (nominal) Chemical composition (nominal) % C Si Mn P S Cr N 0.62 0.2 0.6 ≤0.025 ≤0.010 14 0.11 Heat treatment Hardening data Hardening temperature 1050°C (1922°F), holding time 5 minutes, quenching in oil. Tempering data The following diagram exemplifies the tempering response for Alleima® 14C28N®. More detailed hardening data can be found in the Alleima hardening guide. Strip thickness 2.5 mm (0.098 in.), tempering time 30 minutes. Brittleness and loss of corrosion resistance occur with tempering above 450°C (840°F). The following figures show the importance of using the right hardening conditions to optimize the microstructure and properties. Too high hardening temperature gives coarse structure, high austenite content (30%), few carbides. Consequence: low hardness and bad wear resistance. Too low cooling rate after austenitizing gives carbide precipitations in the grain boundaries. Consequence: brittleness and reduced corrosion resistance. Optimized hardening conditions give optimal austenite content (15%), many uniformly distributed carbides. Consequence: optimal combination of hardness, wear resistance, ductility and corrosion resistance. How the hardening parameters affect the product properties Too high hardening temperature gives low hardness and bad wear resistance due to excessive content of retained austenite. A low hardening temperature gives low hardness and reduced corrosion resistance. Too long holding time at the optimal hardening temperature increases the amount of retained austenite and lowers the hardness. Too short holding time at the optimal hardening temperature has the same effect as low austenitizing temperature. The maximum hardness will be obtained at a retained austenite content of about 15%. Deep freezing, i.e. cooling to below room temperature, increases the hardness by about 1–2 HRC. With deep freezing, the highest possible hardness will be achieved by increasing the hardening temperature. Read more in the Alleima hardening guide. High cooling rate after hardening is necessary to avoid brittleness and reduced corrosion resistance. 600°C (1112°F) should be reached within 1–2 minutes and room temperature within 30 minutes. Rehardening is generally not recommended as it will not give optimal product properties.
