超音速火焰喷涂WC-Co涂层结构的研究

STUDY OF STRUCTURE OF WC-Co COATINGS SPRAYED BY HIGH VELOCITY FLAME

用X射线衍射研究超音速火焰喷涂WC-Co涂层的结构及其影响因素的结果表明,超音速火焰喷涂过程中,WC的分解也会发生,但受WC-Co喷涂粉末结构的影响很大.当粉末中的结合相为复合碳化钨(如Co_3W_3C,Co_6W_6C)而非金属钴时,WC最容易发生分解,依赖于燃气的种类,将分解为W_2C或金属钨.钴包覆WC型粉末喷制的涂层结构明确显示了涂层中CO-W-C非晶态相的形成.Co-W-C三元非晶合金经结晶化热处理后将析出复合碳化物相Co_6W_6C.

The structure of WC-Co coatings sprayed by high velocity flame is studied by X-ray diffraction analysis. The effect of WC-Co powder structure on the structure of subsequent coatings is investigated using five typical types of powders and Jet-Kote spraying process. It is shown that the decomposition of tungsten carbide occurs during high velocity flame spraying. However,the structure of WC-Co powders influences greatly the structure of sprayed coatings. The carbides which are aggregated by eta-phase instead of metallic cobalt are most apt to decompose to metallic tungsten. It is desirable to spray such powder using fuel gas of low flame temperature,such as C3H6 rather than C2H2-riching fuel gas. The carbides in Co aggregated WC powder are most difficult to decompose. Spraying of cobalt clad WC powder clearly revealed the formation of Co-W-C trinary amorphous phase in the coating which will crystallize to metallic phase and complex carbide Co6W6C under heat-treatment of about 873K.