Microstructure and mechanical properties of thermal sprayed nanostructured Cr3C2-Ni20Cr coatings

Abstract

Cr 3 C 2 -Ni20Cr coatings have been used for corrosion and wear resistant applications. However, one of the shortcomings of these coatings is its low hardness, and consequent low wear resistance, for long term high temperature applications. Nanostructured coatings of many materials have exhibited higher hardness and strength compared with conventional coatings of the same material. Consequently, nanostructured coatings of other materials, including Cr 3 C 2 -Ni20Cr have been attempted to enhance overall performance. In this study the effects of high energy milling parameters on Cr 3 C 2 -25(Ni20Cr) powder characteristics as well as the microstructure and mechanical properties of nanostructured Cr 3 C 2 -25(Ni20Cr) coatings formed by high velocity oxygen fuel (HVOF) spraying have been evaluated. The average particle size and crystallite size of milled Cr 3 C 2 -25(Ni20Cr) powders decreased with increase in milling time and this decrease was more pronounced in nitrogen compared to that in hexane. This difference has been attributed to a cushioning effect in the latter medium. The coatings prepared with milled Cr 3 C 2 -25(Ni20Cr) powders had a more uniform microstructure, were harder and had higher relative fracture toughness compared with coatings prepared with as-received powders.

Microstructure, Mechanical Properties and Wear Behavior of High-Velocity Oxygen-Fuel (HVOF) Sprayed (Cr3C2-NiCr+Al) Composite Coating on Ductile Cast Iron

“…Phase analysis performed on the basis of diffraction studies, except for the occurrence of the ceramic phase Cr 3 C 2 and metallic phases NiCr and Al, did not show any new phases formed during spraying ( Figure 5), i.e., carbides Cr 7 C 3 and Cr 23 C 6 , formed in the decarbonisation process of Cr 3 C 2 carbide [13]. X-ray examinations do not confirm the occurrence of these carbide phases because the main diffraction peaks Cr 7 C 3 and Cr 23 C 6 coincide with the lines corresponding to the phases NiCr and Cr 3 C 2 [14]. In addition, the diffraction lines of the revealed phases are not widened, which indicates a low degree of elastic-plastic deformation of the metallic phases, NiCr and Al.…”

Effect of Heat Treatment on the Microstructure and Phase Composition of ZrB2–MoSi2 Coating

“…Y2O3 acts as a stabilizer of high-temperature tetragonal and cubic modification of zirconia [10]. Aluminum acts as a bonding material for the oxidizing agent in the process of spraying and to create "plastic" lamellae and nano-dispersed inclusions, in order to relieve internal stresses [22][23][24]. The powder and fracture surfaces of the samples were investigated using a scanning electron microscope (SEM) (Quanta 600 FEG, FEI Company, Eindhoven, Netherlands) equipped with an EDAX Pegasus 2000 Energy Dispersive X-ray (EDX) (Mahwah, NJ, USA).…”

“…The parameters of the coating spray are listed in Table 1. Y 2 O 3 acts as a stabilizer of high-temperature tetragonal and cubic modification of zirconia [10]. Aluminum acts as a bonding material for the oxidizing agent in the process of spraying and to create "plastic" lamellae and nano-dispersed inclusions, in order to relieve internal stresses [22][23][24].…”

Utilization of mechanically alloyed powders for surface protective coating

“…HVOF of nanostructured Cr 3 C 2 -Ni20Cr coatings Da Cunha et al [4] used wet high-energy ball milling for preparations of Cr 3 C 2 -25(Ni20Cr) powders. They used liquid hexane as milling control agent to reduce the average particle size.…”