Abstract
Electroless Ni-B plating has been tried on steel substrate in an effort to employ low-cost starting materials for electrical contacts or connectors. By selected conditions of heat treatment in a high vacuum environment the plating can acquire Cr-equivalent hardness without the effluents of the hard chromium plating process. The surfaces were characterized under scanning electron microscope and by XRD. The fabricated materials were tested under corrosion conditions by polarization measurements. Semispherical nickel plated steel joints were tested in a computer controlled contact make-break apparatus, under simultaneous application of a mechanical and a low-voltage electrical load for 20,000 cycles. After heat treatment the plating acquires a crystalline structure with very good adhesion to the substrate material. Corrosion decreases and increased hardness is obtained. The surface is also characterized by good electrical properties during aging accelerated tests.
Highlights
Several case studies of electrical failures have shown that environmental contamination slips in between stationary contact joints and settles on or corrodes the electrical contacts^ I All stationary electrical contact types are required to have low stable contact resistance during servicing periods, which may exceed up to 40 years
Metal Madrid Vol Extr. (2005) 232-238 (c) Consejo Superior de Investigaciones Científicas Licencia Creative Commons 3.0 España connectors. It aims to the provision of a corrosion resistant layer with chromium equivalent hardness and stable electrical characteristics in order to be used as stationary, electrical contacts operating in adverse environments
After the heat treatment the deposits exhibit a bright sharp color and acquire an excessive surface microhardness, which is of the order of 1670 HV following the 5 min thermal exposure at 850 °C in a high vacuum
Summary
Several case studies of electrical failures have shown that environmental contamination slips in between stationary contact joints and settles on or corrodes the electrical contacts^ I All stationary electrical contact types are required to have low (of the order of milliohm or less) stable contact resistance during servicing periods, which may exceed up to 40 years. (c) Consejo Superior de Investigaciones Científicas Licencia Creative Commons 3.0 España (by-nc) connectors It aims to the provision of a corrosion resistant layer with chromium equivalent hardness and stable electrical characteristics in order to be used as stationary, (or sliding) electrical contacts operating in adverse environments (i.e. synergy effect of fretting and pollution). Electroless nickel is an engineering coating, normally employed because of its excellent corrosion and wear resistance. The electrical resistivity of these coatings is similar to that of nickel-phosphorus alloys, ranging from 89 |LlQ-cm in the as deposited condition to 43 |lQ-cm after heat treatment at 1,100 °Ct^^l. After heat treatment the wear resistance of electroless nickel-boron is equal or exceeds that of hard chromium coatings
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call