Improvement of hardness and mechanical properties of electroless nickel-boron deposits by thermochemical treatment

摘要

Electroless nickel-boron deposits were synthesised on steel substrate and then submitted to nitrogen based thermochemical treatments. Treatments were carried out between 300 and 600°C, for times up to 10 hours, using conditions very similar to vacuum nitridation or in standard nitriding atmosphere. Micro- and nanohardness measurement were carried out on the free surface of the sample and on polished cross-sections. Vacuum nitrided nickel-boron deposits showed a higher hardness than deposits annealed using the same temperature and pressure conditions under argon. The samples were also investigated by XRD, SEM and optical microscopy to assess the structural and composition changes in the sample during nitridation.