Tribological characterization of electroless nickel-boron coatings.

anocrystalline electroless nickel-boron deposits (on steel substrates) were submitted to heat treatment under non-reactive atmosphere or to nitriding to enhance their properties. Two different nitriding processes were used on the samples: one classical industrial process under an ammonia-based atmosphere and a novel, environment friendly treatment under a reduced pressure, nitrogen-based, atmosphere. The mechanical and tribological properties of the as-deposited and treated samples were investigated by various methods including nanoindentation and scratch tests. Their structural properties were also studied. The hardness of the deposits increased from 900 to 1250 hv 100 due to optimal crystallization after the heat treatment and was further enhanced up to 1600 hv 100 after nitriding. The scratch tests resistance of the coatings was good in both as-deposited conditions as well as after post treatment.