Influence of the heat treatment on the abrasive wear resistance of electroless Ni-P

Electroless Ni-P coatings on plain carbon steel were prepared by using an acid bath based on NiCl2 as source of nickel cations. Heat treatments were performed at 260 degrees and 400 degrees C for 25 h and 1 h, respectively. The abrasive resistances of the coatings which suffered different heat treatments were determined by using the modified bail cratering method, recently proposed by Staia et al. The abrasive media employed was a mixture of 100 ml ethylene glycol and 1 g of 3 mu m diamond paste, A RB38.1/G100P3 ball-bearing was used as tribological pair. The individual wear constants for the substrate and coatings were determined from the recorded plots of the crater depth vs. sliding distances with the aid of theory of the imposed shape wear scar reported in the literature by Kassman et al. Electron microscopy was used to study the morphology of the worn surfaces. As a result, it was found that the heat treatment decreases the abrasive wear resistance of the coatings. A comparison between the methods proposed by Rutherford and Hutchings and ours for assessing the wear constants is carried out, particularly in relation to the relevance of including in the computation the value of the friction force. (C) 1997 Elsevier Science S.A.