CORROSION AND WEAR RESISTANCE CHARACTERISTICS OF LASER ALLOYED NiCr COATING ON CAST IRON LINER

摘要

In order to reduce the E85 fuel induced excessive wear of the cast iron engine cylinder liners, research on laser alloying of NiCr alloy with powder feeding was performed to locally change both the composition and the microstructure. The research indicated that laser alloying of 75Ni25Cr on grey cast iron liner demonstrates good alloying results, the microstructure of the alloyed layer is composed of pre-eutectic austenite and ledeburite. Ni is mainly in the austenite, while Cr is mainly in cementite. The average hardness is HV_(0.2)815. The corrosion resistance of the alloyed layers in diluted H_2SO_4 solution and NaOH solution is dramatically improved compared to the grey cast iron. The relative wear resistance of the laser alloyed 75Ni25Cr layer is 3.07 times of that of the grey cast iron. Laser alloying can be a good solution to improve the grey liner in E85 fuel environment by locally changing both the microstructure and composition of the cast iron liner.