The effect of thermochemical treatment on the structure and hardness of electroless Ni–P coated low alloy steel

In the present research, three groups of the low alloy steel samples include bare steel, thermochemical treated steel and electroless Ni–P coated steel followed by thermochemical treatment were prepared. Surface characterizations such as morphology, present phases, roughness and hardness were evaluated by SEM, EDS, XRD, profilometry and microhardness tests. It is found that the effect of the thermochemical treatment in H2/NH3 mixture on coated samples dependent on the coatings thickness is different. In addition, it is shown that a multicomponent coating containing phosphide, nitride and intermetallic phases as well as diffusion region can be developed in the thin electroless Ni–P coated steel by thermochemical treatment.