| Cr₃C₂-25wt.%NiCr coatings on mild steel substrate by plasma spray process were produced to evaluate microstructural characterization and mechanical properties. As-deposited Cr₃C₂-NiCr coating samples were subjected to two heat treatment conditions such as annealing under H₂ gas circumstance and hot press treated condition. The two heat treated coatings were investigated in terms of microhardness, adhesion strength, wear resistance, surface roughness, porosity formation, and microstructures. The microstructure of as-coated Cr₃C₂-NiCr samples displayed layered structure with 3∼4㎛ thickness and 0.2㎛ grain size. The degree of porosity formation and surface roughness were decreased as increasing temperature range of 400℃∼1200℃, and showing better wear resistance, microhardness and adhesion strength for the annealed conditions. And wear resistance and adhesion strength also were improved as increasing the temperature range of 300℃∼ 700℃ and pressure range of 50MPa∼200MPa for the hot press treated condition. Further, microhardness values were increased as increasing temperature only. It was also indicated that mechanical behaviors and microstructural characteristics of the two heat treated conditions were superior to those of the as-deposited condition according to the comparison studies. |
|
