Effect of NaBH4 concentration on hardness and microstructural properties of electroless deposited St-37 steel

In this study, electroless Ni-B depositions were achieved on the St-37 steel substrates at different NaBH4 concentrations and 950 oC and 1 hour. Electroless Ni-B deposited samples had a cauliflower-like surface texture that makes the electroless Ni-B deposited surface lubricating naturally and as the NaBH4 concentration increased, the grain size decreases in the microstructure. XRD spectra of the sample showed partial amorph region together with the crystalline region. Microhardness testing of the deposited samples were performed with a microhardness tester under a load of 25 g and an indentation time of 10 s. The highest hardness value was obtained in the sample prepared with 1.4 g/l NaBH4 concentration.