Friction and wear of amorphous carbon coated stainless steel under palm methyl ester contained diesel oil

The popularity of plant-based biodiesel has been increasing nowadays. The methyl ester from various resources, such as Palm Methyl Ester (PME), are mixed with petroleum diesel and sold as biodiesel oil. On the other hand, amorphous carbon coatings have also been applied to mechanical components to improve the friction and wear performances such as those used in fuel injection system. This paper discusses the effect of PME and PME-contained diesel oil on friction and wear of amorphous carbon coated stainless steel balls sliding against stainless steel disk. The tests were conducted using a ball on disk tribometer at severe loading conditions. The results show that the wear of amorphous carbon coated ball decreases significantly with the increase of PME concentration in the diesel oil. When the tests were conducted in PME 100% oil, the wear scar diameter reduces 50% for a-C coated ball and 30% for a-C:H coated ball, compared to the wear scar diameter in pure petro diesel oil. Although clear differences in friction coefficients could not be seen, the results indicated that PME contribute to the reduction of wear of the coated ball, drastically. According to this results, the non hydrogenated carbon coating is more suitable to be used in PME contained diesel oil.