Comparing the Effect of Heat Treatment and Plasma-Nitriding on Corrosion Resistance of Ni-B-CNT Electroless Coating with Different CNT Concentration on AISI 4340 Steel

The aims of the work to study the resistance of corr osion and the hardness of plasma-nitrating and heat treatment of coatings with electroless Ni-B-CNT. Various concentration of CNT range, (0, 0.35 and 0.7)g/L in Ni-B-CNT composite was deposit on 4340 steel in electroless immersion. Following the pr ocedure of plating, every samples were plasma-nitrat ing in atmosphere consist of 50% N2-50% H2 , about (400°C), at (2.5h) were compared with those o f annealed one. The electrodes Ni-B-CNT coatings were prepared by using nickel chloride as s ource for nickel, borohydride act as reducing agent and used (MWCNT). Results of micro hardness was show that the higher har dness of (1250HV) was achieved for Ni-B-0.35g/L CNT pla smanitrating formula whereas the greatest hardness of ( 1010HV)was become for sample of Ni-B-0.35g/L CNT heat t rea ed. Resistance of corrosion of Ni-B-CNT composite coating are better, and they become much better with the inc rease of the CNT concentration. Increase too much CNT deposited on th e substrate, leading to a high region of CNT and ag glomeration that occur is very unfavorable to coating, lead resistan ce of the corrosion of the composite coating become s worse. Also, compared between heat treatment and plasma-nitride, results o f that resistance of the corrosion with plasma-nitr iding is better