Abstract
Mo and Al2O3-Mo coatings are fabricated on a low-carbon steel substrate using atmospheric plasma spraying. The microstructure and mechanical properties of two as-sprayed coatings, with a particular focus on the tribological behaviors from room temperature to 300 °C, are comparatively investigated in this study. Microstructural analysis of the coatings shows that the porosity of the Al2O3-Mo coating is higher than that of Mo coating. The addition of Al2O3 particles reduces the coating–substrate adhesion strength. The Al2O3-Mo coating, in comparison to the Mo coating, shows improved mechanical properties, such as hardness and wear resistance. The friction coefficients of both coatings increase with further increases in test temperatures. The friction coefficient of the Al2O3-Mo coating, tested above 100 °C, is lower than that of the Mo coating. The wear failure mechanisms of the two coatings are delamination, brittle fracture, oxidation and adhesion wear. In addition, local plastic deformation was also found in the Mo coating.
Highlights
Molybdenum (Mo) coatings are used to improve underlying materials’ mechanical properties and to decrease their wear
It can be seen that the Mo powder is near-spherical in shape, showing a typical morphology of agglomerating
The Mo and Al2 O3 -Mo coatings were fabricated by atmospheric plasma spraying (APS), using commercial Mo powders and mixed Al2 O3 -Mo powders respectively
Summary
Molybdenum (Mo) coatings are used to improve underlying materials’ mechanical properties and to decrease their wear They show excellent scuffing resistance to abrasive wear, as well as high corrosion resistance [1,2,3]. Plasma-sprayed Mo coatings have a low hardness of 300 HV, which results in very poor wear resistance [8]. The atmospheric plasma spraying (APS) technique endows an Al2 O3 coating with high hardness, outstanding corrosion and good wear resistance, and excellent chemical stability under critical application conditions [12]. Lubricants 2018, 6, 48 expansion (CTE) between Mo (6.7 × 10−6 /K) and Al2 O3 (6.8 × 10−6 /K) could reduce the thermal stress between the two phases boundaries This leads to fewer micro cracks in the material. Al2 O3 dopant, were fabricated using APS, in an attempt to assess the microstructure, mechanical properties and wear behaviors (RT to 300 ◦ C) of the two coatings
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