How to grind thermal spray coating?

When grinding the coating, we should pay attention to the fact that there is a great difference between the forging and casting parts of the same material. Excessive grinding pressure will cause the transfer or movement of particles on the surface of the coating, and even cause cracks in the coating. Due to poor thermal conductivity of the coating, there should be sufficient cooling medium during grinding.

In the grinding process, due to the high hardness of thermal spraying coating, diamond abrasive tools are used for machining, mainly diamond grinding wheel and diamond sanding belt.

The selection of grinding wheel should take into account such factors as coating type, coating hardness and structure, workpiece size, grinding quantity and surface roughness requirements, type, state and capacity of grinding machine, etc. Diamond grinding wheel has durability and can grind all kinds of hard alloy, metal, ceramic and cermet cleanly.

Generally speaking, the finer the spraying powder, the lower the porosity of the coating, the more uniform the coating, the better the finish after grinding.

Factors such as coating type, hardness, workpiece size and shape, grinding quantity, surface finish requirement and grinder type should be considered when selecting grinding wheel. Generally speaking, for wear resistant coating coarse grinding particle size in 125-150 mesh, for fine grinding particle size in 380-400 mesh.

In order to achieve the desired grinding effect, when light grinding pressure or high grinding speed is required, a softer grinding wheel should be used to make the contact area large. When using heavy grinding pressure or require lower roughness, should use a hard level of grinding wheel binder binder type are vitrified bond and thermosetting resin binder Vitrified bond commonly used for metal coating. Can improve the grinding speed and achieve accurate fit tolerance, and not affected by acid oil and water temperature changes. For ceramic coating generally choose resin binder, used for fast grinding and produce low surface roughness grinding wheel abrasive particle size selection to process a lower roughness should be used for grinding wheel with finer sand particles coarse grinding can be used 30-60 mesh particle size, fine grinding 60-120 mesh particle size factors affecting the cutting performance of grinding wheel characteristics are mainly by abrasive. Grain size bond hardness structure grinding wheel width and other factors determine.

1. Abrasive

Abrasive is the main component of grinding wheel. It has high hardness, wear resistance, heat resistance and certain toughness to withstand the cutting heat and cutting force during grinding. Abrasive is the cutting material, it and turning tool materials should have high hardness, high wear resistance, enough bending strength and impact toughness, high heat resistance, etc. At present, green silicon carbide, artificial diamond and cubic boron carbide abrasives are used for grinding high hardness thermal spraying coatings. A lot of experiments show that the performance of artificial diamond wheel is far better than that of green silicon carbide and white corundum wheel.

2. Grit

Grit refers to the size of abrasive particle size.

Particle size is divided into abrasive and micro powder two kinds. The abrasive with particle size greater than 40 μ m is called abrasive grain. Abrasive with particle size less than 40 μm is called micropowder.

The force of grinding wheel has great influence on the roughness and grinding efficiency of grinding surface. Coarse abrasive, grinding depth, high productivity, but the surface roughness value is large. Otherwise, the grinding depth is uniform and the surface roughness is small. So coarse grinding, generally choose coarse particle size, fine grinding choose fine particle size. When grinding soft metal, coarse abrasive grains are used, and when grinding brittle and hard materials, fine abrasive grains are used.

The selection range of particle size of artificial diamond grinding wheel is: