Effect of Isothermal Heat Treatment on Mechanical Properties of WC-17Co Coatings

摘要:

利用超音速火焰喷涂技术在Ni718合金表面制备WC-17Co涂层，然后进行150 ℃/10 h，300 ℃/10 h和450 ℃/10 h恒温热处理。利用纳米压痕和显微压痕的方法研究热处理过程对涂层显微硬度、弹性模量和断裂韧性的影响，利用Almen试片曲率法计算试片中残余应力的变化。结果表明，150，300和450 ℃的热处理过程未对WC-17Co涂层的组织和结构特征造成显著地影响；涂层的显微硬度、弹性模量和断裂韧性随热处理温度的升高而降低；涂层机械性能随温度升高而降低的变化趋势是由涂层残余压应力的变化特征引起的。

Abstract:

WC-17Co cermet coatings were deposited on Ni718 alloys using the high-velocity oxygen fuel (HVOF) technique. These coatings were then heat treated by different processes (150?°C, 10?h; 300?°C,?10?h; 450?°C,?10?h). The effects of heat treatment on microhardness, elasticity modulus, and fracture toughness were studied by an indentation method. The residual stresses of the coated specimens were evaluated by the Almen strip method. The results show that the phase constitution and the structure of the WC-17Co coatings exhibit no obvious change in 150, 300, and 450 °C heat-treatment. The microhardness, elasticity modulus, and fracture toughness of the WC-17Co coatings decrease with the increase of heat treatment temperature. The descent tendency of the mechanical properties is attributed to the decline in compressive residual stresses after isothermal heat treatment.