Ni60CuMoW alloy power was clad on 45 steel surfaces using a synchronization powder feeding method by 6kW
transverse-flow CO2 laser apparatus. The effect of laser power and heat treatment process on corrosion resistance of the
cladding layer was investigated. The microstructure and mechanical property were analyzed by X-ray diffractometer
(XRD), scanning electron microscope (SEM), energy depressive X-ray spectroscopy (EDX), microhardness meter
and PS-268A electrochemical test equipment. The results show that the cladding layer is mainly composed of γ (Ni, Fe),
solid solution (Ni, Cu), compounds Ni31Si12, Cr5B3, CrB, Ni3B, FeNi3, M23C6 (Cr23C6 or (Fe,Ni) 23C6) phase and a small
amount of WC or W2C. With the increase of laser power, corrosion resistance and microhardness has been greatly
improved. Compared with the untreated substrate, the maximum self-corrosion potential of single-pass layer at laser
power 3.2 kW in 3.5% NaCl saturated solution increases by 136.2mV, and the lowest corrosion current density decreases
by 2 orders of magnitude. The mean microhardness of treated samples raises by 5.17, 4.90 and 4.89 times, respectively.
The corrosion potential of multi-pass layer increases by 437.6mV and corrosion current density decreases by one order of
magnitude than that of single-pass layer sample. After temper 600°C heat treatment, the primary dendrite and block (or
needle) eutectic in cladding coatings become more uniform, the maximum self-corrosion potential increases by 45.5mV
and corrosion current density also decreases obviously.
A high-temperature oxidation resistant TiN embedded in Ti3Al intermetallic matrix composite coating was fabricated
on titanium alloy Ti6Al4V surface by 6kW transverse-flow CO2 laser apparatus. The composition, morphology and
microstructure of the laser clad TiN/Ti3Al intermetallic matrix composite coating were characterized by optical
microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer
(EDS). In order to evaluate the high-temperature oxidation resistance of the composite coatings and the titanium alloy
substrate, isothermal oxidation test was performed in a conventional high-temperature resistance furnace at 600°C and
800°C respectively. The result shows that the laser clad intermetallic composite coating has a rapidly solidified fine
microstructure consisting of TiN primary phase (granular-like, flake-like, and dendrites), and uniformly distributed in the
Ti3Al matrix. It indicates that a physical and chemical reaction between the Ti powder and AlN powder occurred
completely under the laser irradiation. In addition, the microhardness of the TiN/Ti3Al intermetallic matrix composite
coating is 844HV0.2, 3.4 times higher than that of the titanium alloy substrate. The high-temperature oxidation resistance
test reveals that TiN/Ti3Al intermetallic matrix composite coating results in the better modification of high-temperature
oxidation behavior than the titanium substrate. The excellent high-temperature oxidation resistance of the laser cladding
layer is attributed to the formation of the reinforced phase TiN and Al2O3, TiO2 hybrid oxide. Therefore, the laser
cladding TiN/Ti3Al intermetallic matrix composite coating is anticipated to be a promising oxidation resistance surface
modification technique for Ti6Al4V alloy.
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