Abstract
To protect aluminum parts in vehicle engines, metal-based thermal barrier coatings in the form of Fe59Cr12Nb5B20Si4 amorphous coatings were prepared by high velocity oxygen fuel (HVOF) spraying under two different conditions. The microstructure, thermal transport behavior, and wear behavior of the coatings were characterized simultaneously. As a result, this alloy shows high process robustness during spraying. Both Fe-based coatings present dense, layered structure with porosities below 0.9%. Due to higher amorphous phase content, the coating H-1 exhibits a relatively low thermal conductivity, reaching 2.66 W/(m·K), two times lower than the reference stainless steel coating (5.85 W/(m·K)), indicating a good thermal barrier property. Meanwhile, the thermal diffusivity of amorphous coatings display a limited increase with temperature up to 500 °C, which guarantees a steady and wide usage on aluminum alloy. Furthermore, the amorphous coating shows better wear resistance compared to high carbon martensitic GCr15 steel at different temperatures. The increased temperature accelerating the tribological reaction, leads to the friction coefficient and wear rate of coating increasing at 200 °C and decreasing at 400 °C.
Highlights
During the last few decades, aluminum alloy replacing steel components has developed gradually for weight reduction of vehicle engines
The relatively low melting point and poor wear resistance of aluminum alloys were compelled to face in application
The inherent brittle characteristic of these materials may reduce the reliability of their coatings, or even cause catastrophic failure under mechanical loading or thermal shock [4,5,6]
Summary
During the last few decades, aluminum alloy replacing steel components has developed gradually for weight reduction of vehicle engines. Thermally-sprayed coatings are considered an effective way to alleviate these issues simultaneously [1,2,3,4], especially for thermal barrier coatings (TBCs). It is well-known that many ceramic as TBCs materials, for instance yttria-stabilized zirconia (YSZ), and display excellent thermal insulating properties and high hardness. There is a rising interest in developing metal-based thermal barrier coatings (MBTBCs) to overcome the defects of ceramic-based thermal barrier coatings (CBTBCs). To restrict the free electron contribution to thermal conductivity of MBTBCs, amorphous metallic coatings exhibit potential applications because of their high densities of scattering defects. Fe-based amorphous coatings seem to be the most promising candidate, mainly consulting the glass-forming ability, wear resistance, and cost efficiency
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