IMPROVEMENT OF WEAR RESISTANCE OF ALUMINUM ALLOY D16 BY DIFFERENT METHODS OF SURFACE HARDENING
DOI:
https://doi.org/10.31734/agroengineering2018.01.153Keywords:
aluminum alloy D16, HVOF, plasma spraying in dynamic vacuum, laser reinforcement, plasma electrolytic oxidation, abrasive wear resistanceAbstract
The paper is devoted to establishing the effect of surface-strengthening processing on the structure and wear resistance of D16 aluminium alloy. The surface was strengthened by the following methods: supersonic gas-flame (HVOF) and plasma spraying of coatings VC–FeCr in dynamic vacuum, laser melting of the surface layers of the alloy with the introduction of SiC disperse powders and plasma electrolytic oxidation.
The coatings was sprayed using the High Velocity Oxygen Fuel Flame Spraying process (HVOF) using the Diamond Jet Hybrid gun and JP5000 gun equipments for high-speed spraying o the coatings. The powder particle velocity, fraction 20...45 mm, was ~ 650 m/s. Vanadium carbide powder, ferrochrome and cobalt alloy with nickel were used for spraying.
For laser surface reinforcement of the D16 alloy, a SiC powder of 80 μm dispersion, a hardness of 2600 HV and a melting point of 2760°C was used. The powder was blown with a spray of argon to a surface layer of samples fused with a laser (Nd: YAG Lazer Rofin Sinar DY 044/022) at a speed of 25 mm/sec. The pre-sample was heated to 170°C.
Plasma electrolyte oxidized layers were formed at the installation of IMPELOM in electrolyte plasma of 3 g/l KOH + 2 g/l nNa2O mSiO2, the remaining distilled water. The current density is 10 A/dm2, the ratio between Ic/Ia = 1, the duration of coating synthesis is 60 min.
The wear resistance of the surface layers was evaluated under conditions of friction with rigid and non-rigidly fixed abrasive particles and compared with wear resistance standards – steel ШХ-15, deposited with PW 80Х20Р3Т layer and a coating obtained by electric arc metallization from powder wire PW 70Х18Р3.
The VC-FeCr-based coating has been found to have a high abrasion resistance, regardless of the type of fuel. During the laser modification of the D16 alloy surface, SiC particles actively interact with the aluminum melt to form Al4C3 carbides. The wear resistance of the laser-reinforced surface, in the condition of a firmly abrasive, is 222 times higher than that of the unstretched. In case of wear with a non-rigid abrasive, the laser reinforcement of the alloy slightly changes its durability. The investigated coatings have the highest wear resistance with plasma-electrolyte oxide layers on the D16 alloy.
It is established that wear resistance of coatings sprayed is 85–100 times higher then D16 base, 4–5 times higher then ШХ15 steel and some what higher then deposited layer from the PW 80Cr20P3Ti. Plasmoelectrolitic oxidation provides the highest wear resistance of the surface layer on D16 alloy, regardless of the conditions of abrasive wear.
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