Influence of manganese phosphating on wear resistance of steel piston material under boundary lubrication condition

The forged steel piston material of 42CrMoA will generate a non-metallic and non-electric conversion film on the surface after the manganese series phosphating (Mn-P) treatment. Compared to the traditional zinc series phosphating (Zn-P) treatment, this type of film is thicker, the coverage rate is higher and the arrangement of crystal particles is better distributed. In order to study the friction and wear characteristics of 42CrMoA after Mn-P under boundary lubrication condition, an abrasion tester was used to simulate the working state of the forged steel piston, the wear surfaces was observed with electron microscope, and finally obtained the friction coefficient, wear rate and wear morphology of the specimens under different conditions. The results show that the friction coefficient and wear rate decrease significantly after Mn-P in poor lubrication conditions, especially under high normal pressures, they decrease by nearly 1 time, and the variation amplitude also decreases obviously with the normal pressure or relative speed changes. The phosphating film can also change the wear mechanism of the matching surface, particularly, in some bad conditions. The adhesive wear may change into slight abrasive wear, and the wear degree of the material was reduced. The surface roughness of metal has a great influence on the effect of phosphating, the smooth surface can form a well-distributed and dense phosphating film, which plays a good role in oil storage and wear resistance. (C) 2016 Elsevier B.V. All rights reserved.