WC-Co复合粉末的原位合成及于硬质合金涂层制备中的应用

Fabrication of Cemented Carbide Coating with In-situ Synthesized WC-Co Composite Powder

目的为解决超细/纳米WC-Co热喷涂时易于脱碳等瓶颈问题,制备具有高的硬度、断裂韧性、耐磨性和表面质量等优异综合性能的超细及纳米结构硬质合金涂层,并推广其在工业领域中的应用。方法以原位合成技术批量制备的超细/纳米WC-Co复合粉末为原料,利用团聚造粒技术制备得到具有高球形度和致密性,并保持原有超细/纳米结构的喷涂喂料粉末,利用超音速火焰喷涂工艺制备低脱碳、高致密的超细结构WC基涂层。结果降低喂料粉末孔隙度可有效减少涂层中W2C等脱碳相的含量,在优化工艺下制备的超细结构WC基涂层的硬度达到1450HV0.3以上,韧性相对于常规微米结构涂层提高40%以上,在两种载荷和磨料条件下均表现出更高的耐磨性。结论利用原位反应技术批量合成的超细/纳米WC-Co复合粉制备的硬质合金涂层具有优良的综合性能,可应用于对涂层的硬度、耐磨性、强韧性配合和表面质量有较高要求的工况。

ABSTRACT： Objective This work aims at solving the problems that the ultrafine/nano WC-Co raw powders were easy to suffer from decarburization during thermal spraying and thus preparing the ultrafine/nanostructured cermet coatings with excel- lent comprehensive properties such as high hardness, toughness, wear resistance and surface quality for extending their applica-tions in industries. Methods The ultrafine and nanoscale WC-Co composite powders were prepared in batch by the in-situ syn- thesis technique. Through a granulation process, the composite powders were agglomerated into the thermal spray feedstock powders, which had good spherical shape and high density while keeping the original ultrafine/nanostructures. After that, the ul- trafine-structured WC-based coating with low decarburization and high density was obtained using the high velocity oxy-fuel spraying. Results The content of W2C in the coating could be greatly decreased by reducing the porosity of the feedstock par- ticles. By optimizing the spray parameters, the prepared ultrafine-structured coating had hardness above 1450 HV0.3, and tough- ness increased by over 40% as compared with the conventional micron-scaled coatings. Thus, the ultrafine-structured coating had better wear resistance at different testing conditions. Conclusion The cemented carbide coatings prepared by using the ultrafine or nanoscale WC-Co composite powders with the in-situ synthesis technique have excellent comprehensive properties. The composite powders are applicable to prepare coatings that meet demands of high hardness, wear resistance, toughness and surface quality as high-quality spraying materials.