The Elevated-temperature Wear Behavior Evolution Of HVOF Sprayed Tungsten Carbide Coatings:Respond To Heat Treatment

Thermal sprayed WC-Co coating is widely used in aerospace,petrochemical,papermaking,metallurgy and other fields,due to its high hardness and good wear performance and corrosion resistance.As a kind of surface modification coating,WC-Co coating can extend the service life and reduce the manufacturing cost of the product.In practical application,the WC-Co coating has to suffer high temperature environment.Furthermore,heat treatment of the metal materials can be used to ameliorate structure and performance in order to acquire excellent properties.Therefore,it`s very necessary to study the influence of the heat treatment on the high temperature friction properties of WC-Co coating.In this work,WC-Co coatings were sprayed by high-velocity oxy-fuel?HVOF?thermal spray.The as-sprayed WC-Co coating was heat treated at different temperatures and different time.And then the high-temperature sliding tests of as-sprayed WC-Co coating and teat treated WC-Co coating were conducted,and the effects of heat treatment on the high-temperature wear properties were investigated.The results show that:?1?Compared with as-sprayed WC-Co coating,the predominant phase of heat treated coatings was WC.WO3 and CoWO4 formed after heat treatment.The heat treatment made the coatings dense.?2?As shown in this work,the best heat treatment temperature was 450?,the optimal heat treatment time was 8h.The average porosity of the as-deposited coatings was approximated to 4.1%.In addition,the porosity decreased with the increase of the heat treatment time.The micro hardness of the coatings heated for 8h was the largest,which could reach 1378.3±41 HV_0.3.?3?For the as-sprayed and heat treated WC-Co coatings,the friction coefficient decreased gradually with the increase of the sliding temperature?350⁵50??.This was due to the the oxidation of the coating.With the increase of temperature,the surface oxidation phase increased gradually,which reduced the friction coefficient of the coatings.?4?For the as-sprayed WC-Co coatings,the wear rate decreases from 350 to450? and increases from 450 to 550?.The minimum wear rate was3.65×10^-6mm³?N^-1m^-1 after sliding at 450?.For the heat-treated WC-Co coatings,the wear rate decreases from 350 to 550?.The wear rate was 2.51×10^-6mm³?N^-1m^-1 after sliding at 450?.Heat treatment could reduce the wear rate of the coating and improve the wear-resisting of the coatings.