Evolution of Nanostructure and Metastable Phases at the Surface of a HCPEB-Treated WC-6% Co Hard Alloy with Increasing Irradiation Pulse Numbers

Self Cite

Abstract:The NiCr-TiB 2 -ZrB 2 composite coating was deposited on the surface of blades made of steel (SUS304) using high-energy ball milling technology and air plasma spraying technology, which aimed to relieve the wear of the blades during operation. The influence of titanium diboride (TiB 2 ) and zirconium diboride (ZrB 2 ) on the microstructure and wear resistance of the coatings was investigated by X-ray diffraction, scanning electron microscopy, Vickers microhardness tester, and a wear tester. The results showed that the TiB 2 and ZrB 2 particles were unevenly distributed in the coatings and significantly increased the hardness and anti-wear, which contributed to their ultra-high hardness and extremely strong ability to resist deformation. The performance of the coatings was improved with the increase of the number of ceramic phases, while the hardness and wear resistance of the coating could reach their highest value when the TiB 2 and ZrB 2 respectively took up 15 wt.% of the total mass of the powder.

Section: Powder Preparationmentioning

confidence: 99%

Composition versus Wear Behaviour of Air Plasma Sprayed NiCr–TiB2–ZrB2 Composite Coating

Zhang

Guan³

et al. 2018

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“…Thus, local spalling and excessive wear on the bearing surface will damage the integrity of the structure. If no effective measures are taken, the expected service life will be significantly shortened with the accumulation of friction effect, even resulting in the failure of the whole machine and even industrial accidents [1][2][3][4]. Up to now, there have been few reports on surface treatment of high-strength structural steel parts with improved surface performance.…”

Section: Introductionmentioning

confidence: 99%

Evolution of Microstructure at the Surface of 40CrNiMo7 Steel Treated by High-Current Pulsed Electron Beam

Qiu

Zhai

et al. 2020

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High current pulsed electron beam (HCPEB) has recently been developed as an effective technique of material surface modification. In this research, a self-developed HCPEB equipment (HOPE-I) was adopted to perform surface modification on quenched and tempered 40CrNiMo7 steel. A composite nanometer structure was formed on the modified surface layer, and the martensite transformation and the dissolution and fracture of cementite can be observed. After initial irradiation, the high cooling rate caused the formation of nanocrystalline on the surface. With continuous irradiation treatments, the cooling rate gradually reduced, while the carbon kept dissolving and ended with surface composition homogenization. Both competitive factors result in the evolution rule of nanometer dimensions of surface structure. After HCPEB treatment, the average size of austenite phase on the modified surface decreased from micron-sized to nanoscale. The corrosion rate decreased from 0.12 mm/a to 0.02 mm/a, showing remarkable improvement of corrosion resistance. The main factors of the improvements of corrosion resistance property are the flat, dense structured and preferred crystal orientation on the modification layer of the treated material surface.

“…The cobalt-based alloys (such as Stellite 6 or Stellite 12) consist of fcc cobalt-based dendrites with interdendritic lamella of Cr-rich carbides, which provide the alloy with the hardness to resist CE [1]. Multiphase materials composed of a metallic matrix reinforced by the distribution of hard particles are also extensively used to enhance toughness and hardness [2,3] and to improve the resistance of CE [4], wear [5], and slurry erosion [6].…”

Section: Introductionmentioning

confidence: 99%

Effects of Cobalt Content on the Microstructure, Mechanical Properties and Cavitation Erosion Resistance of HVOF Sprayed Coatings

Bai

Chen

et al. 2019

Cobalt-based alloy coatings and WC-Co-based ceramic–metal (cermet) coatings have been widely used because of their desirable mechanical properties and corrosion resistance. In this work, the influence of Co content on the microstructure, mechanical properties and cavitation erosion (CE) resistance were investigated. A cobalt-based alloy coating, a WC-12Co coating, and a WC-17Co cermet coating were deposited by high-velocity oxygen fuel (HVOF) spraying on 1Cr18Ni9Ti substrates. Results indicate that the cobalt-based alloy coating had the largest surface roughness because surface-bonded particles of lower plastic deformation were flattened. The existence of WC particles had led to an increase in hardness and improved the fracture toughness due to inhibit crack propagation. The pore appeared at the interface between WC particles, and the matrix phase had introduced an increase in porosity. With the increase in Co content, the cohesion between matrix friction and WC particles increased and then decreased the porosity (from 0.99% to 0.84%) and surface roughness (Ra from 4.49 to 2.47 μm). It can be concluded that the hardness had decreased (from 1181 to 1120 HV0.3) with a decrease in WC hard phase content. On the contrary, the fracture toughness increased (from 4.57 to 4.64 MPa∙m1/2) due to higher energy absorption in the matrix phase. The WC-12Co and WC-17Co coatings with higher hardness and fracture toughness exhibited better CE resistance than the cobalt-based alloy coating, increasing more than 20% and 16%, respectively. Especially, the WC-12Co coating possessed the best CE resistance and is expected to be applicable in the hydraulic machineries.