Optimized Microstructure and Properties of Cr 3 C 2 -NiCr Cermet Coating by HVOF/Laser Hybrid Processing
- PDF / 2,734,338 Bytes
- 9 Pages / 595.276 x 790.866 pts Page_size
- 46 Downloads / 169 Views
PEER REVIEWED
Optimized Microstructure and Properties of Cr3C2-NiCr Cermet Coating by HVOF/Laser Hybrid Processing Enwei Qin1 • Bo Wang1 • Wenli Li2 • Wan Ma1 • Haifeng Lu1 • Shuhui Wu1
Submitted: 28 January 2019 / in revised form: 14 May 2019 / Published online: 30 May 2019 Ó ASM International 2019
Abstract Thermal spraying has been widely used to obtain functional surface coatings against wear or corrosion in various industrial fields. However, pores and low bonding strength are the two inevitable drawbacks for thermalsprayed coatings. In this study, a hybrid process combining thermal spraying with laser beam irradiation was employed to solve the drawbacks. A Cr3C2-NiCr cermet coating was processed successively by high-velocity oxygen-fuel spraying and laser remelting. A fully dense remelt layer without any cracks was successfully obtained. The remelt layer was composed of fused steel base metallurgically bonded with cermet coating, showing a transverse gradient microstructure in aspects of chemical composition and grain shapes. On the top surface, chemical composition and phases from the original coating were preserved, contributing to the enhanced properties of electrochemical corrosion and wear resistance. The improvement was discussed in terms of structure densifying and homogenization. The enhanced properties by the HVOF/laser hybrid process indicate promising application in industrial fields. Keywords cermet coating HVOF hybrid process laser remelting
& Wenli Li [email protected] 1
Suzhou Nuclear Power Research Institute, Suzhou 215004, China
2
School of Mechanical and Electric Engineering, Soochow University, Suzhou 215123, China
123
Introduction In the industrial application of mechanical components for wear or corrosion resistance, metal/ceramic composite materials, i.e., cermets, have always been a priority solution because of the optimized alloy design. However, it is relatively difficult to obtain such cermet composites by conventional means such as powder or ingot metallurgy. Instead, surface technology such as thermal spraying (Ref 1, 2) or cladding (Ref 3, 4) is resorted to fabricate functional coatings on the mechanical component to protect surface from wear or corrosion degradation. High-velocity oxygen-fuel spraying (HVOF) has been one of the most useful industrial choices to produce various cermet coatings (Ref 5-7). In HVOF processing, a fuel such as kerosene is combusted with oxygen in a high-pressure chamber to form a flame with temperature about 3000 K. The feedstock powder is injected into the combustion chamber to reach a molten or half-molten state and accelerated to a velocity of 3-5 times the sound speed, and then impinges on the substrate surface in the final form of splats. Because of the intermediate flame temperature and fairly high velocity of the in-flight particles, lower porosity of *1% and acceptable bonding strength of * 70 MPa can be achieved. However, it is obvious that complete elimination of the coating pores is almost impossible in the particle flattening pro
Data Loading...
