Influence of alloying element additions on tribological behaviour of sintered steels with high content in manganese–nickel

Manganese and nickel are alloying elements with a high hardenability. Manganese is an excellent substitute for nickel due to its low cost but presents a great affinity for oxygen. In this work, the friction and wear behaviour of sintered manganese–nickel steels, by a pin-on-disk test has been studied. The tests were made under dry conditions, 0.1 m/s and 10 N as linear speed and applied load, respectively. Wear behaviour was evaluated against spherical pin of martensitic stainless steel (49 HRC). High manganese–nickel sintered steels were manufactured with two levels of carbon: 0.3 and 0.7% by weight. The unique level of addition of pure electrolytic manganese and different prealloyed manganese–nickel (80Mn/20Ni, 55Mn/45Ni and 25Mn/75Ni) was 4% by weight. All the compositions were prepared by dry mixing in ball mill and compacted at 700 MPa using uniaxial pressing. The sintering was carried out at 1230 °C in 90N2/10H2 as protective atmosphere. Density, porosity and hardness were evaluated. After sintering, all samples were polished at the same surface conditions and friction coefficients and wear rates have been measured. A complete microstructural study of the different steels and their transversal wear tracks was carried out. Deformations of ferritic areas, closed surface porosity and austenite–martensite transformation during wear test were detected. For materials with 0.7% C, the combined effect of carbon and manganese increases wear resistance.