Evaluation of ferrous powder thermal spray coatings on diesel engine cylinder bores

In order to reduce weight, a new liner-less technology without cast iron liner is anticipated to be put into practice in the field of aluminum cylinder block manufacture. Our target is diesel engines. However, diesel fuel contains the element sulfur which introduces the possibility of corrosive attack since sulfuric acid generated on the liner surface is higher than with gasoline fuel. Because of this disadvantage, higher wear and corrosion resistances of the inner surface of the cylinder bore are required to make practical a liner-less aluminum cylinder block. A newly developed ferrous powder (Fe–C–Ni–Cr–Cu–V–B alloy) revealed most excellent corrosion and wear resistances, compared with currently used bulk casting materials such as Fe–C–Si–B alloy and Fe–C–Si–Mo–B alloy for cylinder liners. To test the new ferrous alloy powder it was applied to actual engine bores by using Rota-Plasma spray coating. The results of the experiment showed a potential equivalent to current liner-equipped engine bores.