Effect of carbon nanotubes on microhardness and adhesion strength of high-velocity oxy-fuel sprayed NiCr–Cr₃C₂ coatings

Abstract

NiCr–Cr3C2 coatings are widely used for high temperature and tribological applications due to their high hardness, oxidation, and wear resistance properties. In the present investigation, an attempt is made to further enhance the hardness and adhesion strength of NiCr–Cr3C2 coatings by reinforcing them with multi-walled carbon nanotubes. The carbon nanotubes (3–7 wt%) with varying weight percentages were mixed with NiCr–Cr3C2 using a planetary ball rolling mill and sprayed on SA213 T12 (T12 alloy steel tube) using a high-velocity oxy-fuel spraying process. The microstructures of mixed powder, coating cross-section, and fractured coating surface were characterized using a scanning electron microscope while X-ray diffraction was used for phase identification in the fractured coating surface. The coated samples were subjected to microhardness and adhesion strength tests according to ASTM E384 and ASTM D4541-09 standards. Out of all coatings, NiCr–Cr3C2/7% carbon nanotube composite coating showed the lowest porosity of 1.17%, highest microhardness, and adhesion strength of 563.8 HV and 55.8 MPa, respectively. A fracture analysis after a pull-off adhesion test revealed adhesion failure for NiCr–Cr3C2 coating and combined adhesion/cohesion failure for NiCr–Cr3C2/7% carbon nanotube composite coating.

Neoteric Semiembedded β-Tricalcium Phosphate Promotes Osteogenic Differentiation of Mesenchymal Stem Cells under Cyclic Stretch

“…The coherence and adherence of the β-TCP layers were tested by embedding a nano-β-TCP coating in the middle of two preprepared semicured PDMS and evaluating the bonding ability of the coating to the substrate material by increasing the tensile force until the coating was peeled off from the substrate …”

“…The coherence and adherence of the β-TCP layers were tested by embedding a nano-β-TCP coating in the middle of two preprepared semicured PDMS and evaluating the bonding ability of the coating to the substrate material by increasing the tensile force until the coating was peeled off from the substrate. 14 Friction and wear tests were conducted using a high-speed friction and wear tester (MFT-R4000, TakTark, China). The applied load was 10 N, the sliding time was 20 min, the sliding distance was 5 mm, and the frequency was 1 Hz.…”

Influence of Spraying Parameters on the Structure and Tribological Properties of Cr3C2-NiCr Detonation Coatings

“…Coatings based on Cr 3 C 2 -NiCr are used to protect the surface of parts operating at high temperatures and in corrosive environments from corrosion and wear [1,2], which is provided by the ability to bind the solid phase of Cr 3 C 2 carbide with the NiCr matrix and to create a high density of the coating material [3,4]. Various spray technologies are used for coating deposition: atmospheric plasma spraying (APS), high velocity oxygen fuel spraying, air-fuel spraying (HVOF, HVAF), and detonation spraying [5][6][7][8].…”

Hot-corrosion behaviour of CNT reinforced Cr3C2-NiCr coatings working under high-temperature sprayed by HVOF method

“…5 Kuruba et al reported on CNTs dispersed uniformly between the coating matrix and the fill pores gap, achieving the highest adhesive strength and micro-hardness of 7 wt% of CNTs added in NiCr-Cr 3 C 2 coatings. 6…”

“…5 Kuruba et al reported on CNTs dispersed uniformly between the coating matrix and the fill pores gap, achieving the highest adhesive strength and micro-hardness of 7 wt% of CNTs added in NiCr-Cr 3 C 2 coatings. 6 Chen et al investigated the blended powder coatings and found they exhibited minimum porosity, a dense microstructure, and no cracks compared to the Al-TiB 2 coatings. 7 Sharma et al reported an oxygen flow rate increase from 200 to 250 LPM, enhancing wear rate, fracture toughness, and microhardness.…”