Microstructure and Properties of Tungsten Carbide Coatings Sprayed with Various HVOF Spray Systems

Abstract

The paper reports a series of experiments with various HVOF spray systems (Jet Kote, Top Gun, Diamond Jet (DJ) Standard, DJ 2600 and 2700, JP-5000) using different types of WC-Co and WC-Co-Cr powders. The microstructure and phase composition of powders and coatings were analyzed by optical and scanning electron microscopy and X-ray diffraction. Carbon and oxygen content of the coatings were determined in order to study the decarburization and oxidation of the material during the spray process. Coatings were also characterized by their hardness, bond strength, abrasive wear and corrosion resistance. The results demonstrate that the powders exhibit various degrees of phase transformation during the spray process depending on the type of powder, the spray system and the spray parameters. Within a relatively wide range, the extend of phase transformations has only little effect on coating properties. Therefore coatings of high hardness and wear resistance can be produced with all HVOF spray systems when the proper spray powder and process parameters are chosen.

Effect of roughness on the wear behavior of HVOF coatings dry sliding against a friction material

“…WC-Co-based coatings obtained by thermal spray are widely used in mechanical applications where a high resistance to sliding wear is required [11][12][13]. In particular, high velocity oxy-fuel (HVOF) thermal spraying is regarded as one of the best methods for depositing conventional WC-Co feedstock powders [14][15], in view of the good combination of higher deposition rate and lower temperature with respect to plasma deposition. These conditions determine a lower porosity and, therefore, a better wear resistance of the coatings [13][14][15].…”

“…In particular, high velocity oxy-fuel (HVOF) thermal spraying is regarded as one of the best methods for depositing conventional WC-Co feedstock powders [14][15], in view of the good combination of higher deposition rate and lower temperature with respect to plasma deposition. These conditions determine a lower porosity and, therefore, a better wear resistance of the coatings [13][14][15]. The HVOF WC-Co-based coatings in the as-sprayed condition normally display a hardness in the range 1100-1200 HV, and a surface average roughness, R a , around 5 m, depending on the powder particles size and morphology and on the specific spraying parameters [16][17][18][19][20][21].…”

Corrosive Resistance of HVOF WC Coatings with a Different Binder

“…The decarburization reaction is not favorable but always occurs at facing of high temperature. More details concerning decar-burizeation of WC based coatings can be found in Ref [14][15][16][17][18]. In this study, the test results showed that the use of different binders could not achieve different results in decarburization.…”

Thermal Spray Coating Applications in Tribology: Recent Case Studies

“…Due to the low porosity, highly adherent coatings, and less oxide content, HVOF is the preferred thermal spray process for the chrome replacement. For the deposition of conventional Cr3C2 -NiCr feedstock powders, the HVOF thermal spray process considered the best method as the very high velocity of the flame shortens the time of interaction between flame and the powder [8]. It was concluded that CrC-NiCr HVOF coatings are superior in performance comparing to chrome plating.…”