Development of WC-Co Coatings Deposited by Warm Spray Process

Abstract

The high-velocity oxy-fuel (HVOF) process is commonly used to deposit WC-Co coatings. There are some problems with this process; especially the decomposition and decarburization of WC during spraying make a coating brittle. To suppress such degradation, the warm spray (WS) process was applied to deposit WC-Co coatings, which is capable of controlling the flame temperature in the range of 500-2000°C. The microstructure and phases of the deposited coatings were characterized by using SEM and XRD, and the mechanical properties such as hardness, fracture toughness, and wear properties were also investigated. WS process successfully suppressed the formation of the detrimental phases such as W 2 C and W, which are usually observed in HVOF coatings. The WS coatings showed the similar trend of the hardness variation for Co content with a sintered bulk material. Improvement of toughness and wear behavior was also observed in WS coatings.

Effects of Particle Strength of Feedstock Powders on Properties of Warm-Sprayed WC-Co Coatings

“…Many studies have shown the effects of these phases on the properties of the coatings (Ref 3 -7). Many efforts, therefore, have been made to deposit WC-Co coating in lower temperature ranges than those of HVOF process to suppress the decarburization and decomposition of WC by using highvelocity air fuel (HVAF), cold spray, pulsed gas dynamic spraying (PGDS), and Warm spray (WS) processes (Ref [8][9][10][11][12][13][14][15]. These coatings show no/little detrimental phase transformation and decarburization of WC.…”

Effect of Powder Characteristics on Properties of Warm-Sprayed WC-Co Coatings

“…Many efforts have been made to deposit WC-Co coating in lower temperature ranges than those of HVOF process in order to suppress decarburization and decomposition of WC phases by using high-velocity air fuel (HVAF), cold spray, pulsed gas dynamic spraying (PGDS), and Warm spray (WS) processes (Ref [8][9][10][11][12][13][14][15][16][17][18]. These coatings show no/little detrimental phase transformation and decarburization of WC.…”

Current Status and Future Prospects of Warm Spray Technology

“…Microstructure and mechanical properties of WS coatings have been investigated (Ref 4,(6)(7)(8)(9)12,15,17,19,20) for materials such as titanium, copper, aluminum, metallic glass, WC-Co cermet, nano-grain titanium oxide, UHMW-PE, and PEEK. Among them, titanium and WC-Co have been most extensively studied due to their potential application importance and sensitivity to thermal degradation.…”

“…Since the first papers on warm spraying (WS) were published in 2006 (Ref 1, 2), significant efforts have been made to understand its process fundamentals as well as to explore potential advantages of coatings made by the process for industrial applications (Ref [15][16][17][18][19][20]. Various thermal spray processes are classified schematically in terms of particlesÕ temperature and velocity on a so-called process map as shown in Fig.…”