Changes in the structure and properties of cylinder sleeves of internal combustion engines after laser treatment

Conclusions

• 1. With a high rate of crystallization from the liquid state one finds FeO, Fe₂O₃, and Fe₃O₄ (total concentration ∼40%), 10% austenite, 30% cementite, and 20% martensite in a layer 0.1 μm thick on the surface of SCh24-44 gray cast iron. At a depth of ∼1 μm the austenite and martensite comprise 20% and cementite the remainder.

• 2. X-ray analysis showed that in addition to cementite austenite, and martensite the cast iron also contains metastable phases, austenite, and ε phase after laser treatment, although the intensities of the reflections decrease sharply after tempering at 300°.

• 3. A layer as deep as 50 μm contains 8–10% C, which points to saturation of the solid solution with carbon not only with solution of graphite but also from the carbon-containing paint applied to blacken the surface before the laser treatment.

• 4. The hardness of the melted zone is H₅₀ 1000–1200, the hardness of the heat-affected zone H₅₀ 800–1100.

• 5. Bench tests for 50 h showed that the laser treatment of cylinder sleeves of gray cast iron SCh24-44 in V engines increases the wear resistance to the level of cylinder sleeves with Niresist inserts.