Low carbon steel were coated by hot-dipping into a molten bath containing Al-2 wt%Mn, Al-9wt%Mn, Al-13wt%Mn, respectively. The phase composition, morphology and the adhesion of the aluminide layer were characterized by XRD, SEM, EDAX, OM and scratch tester. The results show that the coating layers is mainly composed of Al, FeAl3, Fe2Al5 and MnAl6 phase. The coatings consists of two-layers structure, i.e., topcoat Al-Mn alloy layer and tongue-like intermetallic compound, and the coating layer is about 800 μm thick. The adhesion of the Al-Mn alloy coatings were characterized by Lc value and were found to be about ~30N. The adhesion gradually decrease with the increase of the Mn contents in alloy coatings.
Using laser cladding technique, Ni3(Si Ti) matrix composite coatings reinforced by in-situ synthesis (Ti,W)C multi-ceramics were fabricatcd by preplacing Ni78Si13Ti9( at%)powders containing different WC contents on the nickel-matrix superalloy substrate. The phases of coatings were investigated by scanning electron microscopy (SEM), X-ray diffractometer (XRD) and electron probe microanalysis (EPMA). Phases of the coatings mainly composed of Ni3(Si Ti), (Ti,W)C multi-ceramics A chemical reaction between WC particle and Ti powder occurs during the laser process, therefore (Ti,W)C was formed.
Porous nanocrystalline thick Ti (CxN1-x) films which bond firmly to the substrate are obtained on commercially pure titanium and Ti6Al4V alloy by plasma electrolytic carbonitriding (PECN) treatment. The microstructures and compositions of the modified layer on different substrates were compared. The results showed that the modified layer is composed of the outer Ti (CxN1-x) film and the diffusion layer. When discharge-treated for 150 min, the thickness of the Ti (CxN1-x) film is ~15μm, irrespective of the different substrate. The TiH2 riched diffusion layer which is 40-45μm thick is located beneath the Ti (CxN1-x) film for the pure titanium substrate, while for Ti6Al4V alloy it is the β-Ti-riched layer which is ~100 μm thick.
In this paper studies the effect of the temperature of boronized layer, holding time and formula of accelerant on the microstructure and properties boronized layer. The result shows that the thickness of boronized layer increases with the increasing of temperature of boronized layer and the holding time expansion. In the experiment, the research contrasts the effect of five groups of boron-sulphurizing rare earths co-cementation and finds that the best effect is to add 1.5% sulfide and 5% rare earth in reagent. The metallographic analysis and hardness testing show that the properties of boronized layer have improved evidently.
Effects of different impact angles such as 45°and 90°on the erosion-abrasion properties of hypereutectic Al-Mn alloy and its composites reinforced with Al2O3 particulates were studied by rotating erosion-abrasion test, and the microstructure and the worn surfaces were analyzed. The results show that the as-cast Al-Mn alloy is composed of aluminium-manganese solid solution, MnAl6 and Al11Mn4 phase, while the δ-Al2O3 particles are included in the composites besides the aforementioned microstructures. With elongating the erosion time, the wear rates of the Al-Mn alloy and its composites increase at the impact angle of 90°, whereas they firstly increase and then decrease , and there is a maximum at 45°. The distortion wear caused by the normal stress is dominant at 90°, which lead to the erosion pits on the worn surface. However, the cutting wear by the shear stress is predominant at 45°, which result in the ploughs.
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