Study On The Interface Between Diamond And Cemented Carbide And Deposition Of High-strength Adhesive Diamond Films

Cemented carbide-diamond coated tools have a very broad application prospects in precision machining of high-strength and hardness materials,but the industrial production of cemented carbide-diamond coated tools is limited by the adhesion between coating and substrate.In order to deposition diamond films with high adhesion,the interface between diamond and cemented carbide is studied firstly,and the specific conditions of interface bond are studied by using modern testing instruments,which makes the research more perfect.Secondly,in order to make the characterization and analysis of adhesion more reliable,the scratch test reliability was studied.Finally,the composite pretreatment process of cobalt removal and sand blasting was used to pretreat the substrate,and diamond films with high adhesion were deposited.The main research results and conclusions of this paper are as follows:There are a large number of cobalt particles in the without cobalt removal nucleation sample.Amorphous carbon and graphite are the main forms of diamond nucleation at the presence of cobalt particles at the interface,while diamond is formed at the interface without cobalt particles.The existence of diamond nucleation layer at the interface bond is a mixture of diamond and graphite or amorphous carbon,which results in poor adhesion.It is presumed that the mechanism of cobalt particles falling off and diffusing at the interface is that methane first adsorbs around the cobalt particles,then permeates into the cobalt particles,and eventually precipitates around and below the cobalt particles to produce graphite or amorphous carbon,thus exerting a supporting force on the cobalt particles to make them fall off and diffuse.The cobalt removal nucleation sample is characterized by less cobalt content,diamond formation at the interface junction,a small amount of amorphous carbon or graphite,which improves the adhesion of the film.However,the excessive cobalt removal will reduce the adhesion due to the porous layer left by cobalt removal pretreatment and the smaller contact area between the interface and diamond.Therefore,in order to improve the adhesion,first of all,cobalt removal pretreatment must be carried out,but need to find a proper depth of cobalt removal,to avoid excessive cobalt removal treatment will make the adhesion worse.In scratch test,the diamond scratch indenter can only be tested two or three times.The repeated use of the scratch indenter will cause serious virtual high,and the lower the adhesion of the sample itself,the more serious the virtual high.However,the relative size of the adhesion between the samples remains unchanged and the relative change trend becomes weaker.Therefore,the scratch indenter used in this paper is only used once to obtain more reliable adhesion characterization data.Through the composite pretreatment process of cobalt removal and sand blasting,the substrate was treated by sand blasting process with 0.4MPa blast pressure,75 mm blast distance,90°blast angle and 90 seconds blast time,then treated with Makarami reagent alkali at 30℃ for 20 minutes,and treated with Caro’s acid reagent for 20 seconds.The high adhesion diamond film with about 60 N was prepared.