Machining Characteristics of Thermal Spray Coatings

       1) Large shock and vibration during processing



    Due to the unevenness of the outer surface of the thermal spray coating, the unevenness of its internal hardness, and the hard spots and pores in the thermal spray coating, the cutting force during processing will fluctuate, resulting in a larger machining process. Shock and Vibration. This requires the rigidity of the machine tool-fixture-workpiece-tool process system to be better. Higher requirements are placed on the strength of the blade (or grinding wheel grit).

    2) The tool is prone to chipping and abnormal wear

    Hard spots (carbides, borides, etc.), blisters, pores, etc. inside the thermal spray coating, coupled with the vibration and impact load during the cutting process, cause the blade or grinding wheel to collapse.

    3) Tool durability is low

    Thermal spray coatings generally have high hardness and wear resistance, and generate large cutting force and cutting heat during processing. For example, when turning Ni60 high-hardness coating, the cutting force is 30%~60 higher than that of 45 quenched steel, and the cutting temperature is higher than that of 45 quenched steel, which accelerates the wear of the blade or grinding wheel grit and makes them quickly dull. This brings great difficulty to the cutting process, and it is even difficult to perform the cutting process. Due to the low tool durability, the increase in cutting amount is limited and the production efficiency is reduced.

    4) Thermal spray coating is easy to peel off

    The bonding strength between the thermal spray coating and the substrate is not high. The coating obtained by spraying is mechanically bonded with the substrate, and the bonding strength is generally 20MPa~70MPa; in addition, the thickness of the coating is generally thin. Therefore, in the During cutting, when the cutting force exceeds a certain limit, the coating is easy to peel off, which should be avoided during cutting.

    5) The heat generated by the thermal spray coating grinding process is large

    When the thermal spray coating is ground, the surface is easily burned and cracked due to the large amount of heat generated, so pay attention to the use of cooling lubricants.