Influence of heat treatment on microstructure and mechanical properties of iron-based coating

Iron-based alloys were deposited on the low carbon steel by plasma cladding process. Furnace annealing was conducted at 600 °C for 40 min. Resulting microstructure and phases were observed and investigated by scanning electron microscopy (SEM), energy-dispersive spectrometer (EDS) and X-ray diffraction (XRD). Effect of post heat treatment on the mechanical properties of coatings was also studied by instrumented indentation technique. It was found that solid solution γ-(Fe, Ni, Cr) and carbide reinforced phases Cr7C3 were the main phases of as-cladding coatings while iron carbide became the main carbide reinforced phase for annealed coatings. For all coatings, hardness and reduced elastic modulus showed obvious load dependence, namely decreased with the indentation load increasing. It was found that calculated values of annealed coatings were generally lower than those of as-cladding coatings as a result of the dissolution of the eutectic structure which decreased the effect of dispersion strengthening.

Research highlights
► γ-(Fe, Ni, Cr) and Cr7C3 are the main phases of as-cladding coatings.
► Eutectic structure partly dissolute after annealed at 600 °C for 40 min.
► Both hardness and modulus show obvious load dependence by nanoindentation.
► Variations in microstructure result in the range of mechanical properties.
► For all specimens, mechanical properties show the same distribution.