Investigation On The Electrical Contact Strengthened Adhesive Coating On Surface Of Steel Substrate

Nanomaterials,due to the small grain size,its strength,hardness and wear resistance are better than general materials.So nanomaterials are now used in many surface technology.WC-Co is a kind of common hard alloy material.However,Co is expensive and rare.So it is very necessary and important to obtain a new material to replace WC-Co.WC-AL2O3 is a new kind of composite material,some researches have showed that WC-AL2O3 composite powders have high value of hardness and toughness,it may probably be used as coating material.Accordingly author deposited WC-AL2O3-Co composite powders on surface of steel substrate by using air spraying method instead of thermal spraying to form coatings,and then the electrical contact strengthened equipment was used to remelt the coatings and form an enhancement layer,which leads to the metallurgic combination between enhancement layer and substrate.So the bonding strength as well as the mechanical properties were improved.Main works completed and conclusions summarized in this article are presented as follows:1.Prepared WC-AL2O3-Co steady slurry by using dry grinding and wet milling.2.Explored the effect of wet milling of dispersion process on the stability of WC-AL2O3-Co spraying slurry.3.Analyzed the effect of spraying process,content of binder on the coatings uniformity,adhesive force and conductivity.4.Optical Microscope(OM)was used to observe the metallographic of the enhancement layers.Scanning Electron Microscopy(SEM)and X-ray diffracmeter(XRD)were employed to analyze the microstructure and phase constitution of the enhancement layers,respectively.5.Thermal shock resistance and microhardness test were employed to analyze the mechanical properties of strengthened layer.6.Compared the mechanical properties of electrical contact strengthened nano WC-14.3%wtAL2O3-1%wtCo caotings,nano WC-12%wtCo coatings and micro WC-12%wtCo thermal spraying layers.The analysis results show that WC?AL2O3,Co powders mixed by dry grinding could be dispersed into steady slurry through wet milling.Steady slurry and suitable spraying method can deposite uniform coatings on steel substrate.After electrical contact strengthening,The element diffusion occurs in the interface between substrate and coatings and new phases are formed in electrical contact strengthened process,the metallurgic bonding is formed between enhancement layers and base.both WC-AL2O3-Co and WC-Co electrical contact strengthening layer have higher microhardness and more excellent performance of thermal shock resistance than WC-Co thermal spraying layer;replacing some Co with AL2O3 can enhance the microhardness,but has lower performance of thermal shock resistance than WC-Co electrical contact strengthening layer.