Diamond smoothing

Plastic deformation of the metal leads to smoothing of the microcrests of the treated surface and the filling of the microprofile cavities with the volume of the deformed scallops.

The use of natural diamonds for processing PPD qualitatively changes this process. It is possible to obtain an exceptionally high class of surface cleanliness on almost all ductile metals and alloys of any hardness. The force with which the process of smoothing with diamond is carried out makes it possible to process thin-walled and low-rigid products, while the surface layer is hardened and residual compressive stresses are formed in it. All this becomes possible due to the exceptional physicomechanical and operational properties of diamond as an instrumental material.

A number of works by domestic and foreign authors are devoted to the research of the process of smoothing the product with diamond tools. The first studies of the process were carried out by I. Hall.

Hall used a diamond tool with cylindrical and spherical work surfaces to study the smoothing process. Hall studies have shown that in the process of ironing directly in front of the tool on the sides and underneath, compression and plastic deformation of the metal occurs, which after the tool passes is unloaded from stresses not exceeding the elastic limit . The depressions located between the ridges of microroughnesses, if they are not very deep, are filled with the metal of the ridges flowing as a result of the impact of the tool. In Figure 1 ? the solid and dashed lines show the relative position of the tool traces remaining on the surface of the product in two subsequent passes.

Diamond has a high thermal conductivity . Its thermal conductivity coefficient is more than two times higher than the thermal conductivity coefficient of VK8 hard alloy , five times higher than that of P18 steel and T15K6 alloy , tens of times higher than the thermal conductivity coefficient of mineral ceramics. The high thermal conductivity of diamond when used as a tool material provides good heat removal from the processing zone, as a result of which comparatively lower temperatures occur on contact surfaces than when ironed with other tool materials. A favorable thermal regime in the contact area is also created due to the high heat capacity of diamond.

A diamond crystal has a low coefficient of friction on a metal surface (about 0.05). Exceptionally high purity, with which its working surface can be polished , extreme strength and wear resistance , make diamond an indispensable tool material for smoothing.

Vibrodynamic rolling. The basis of this process of forming regularly located recesses, in contrast to the previously considered, is not cutting, but cold plastic deformation of the processed material. The main feature of this method is the combination of rolling action, characteristic of most methods of surface plastic deformation (PPD), with shock. As a result, the proportion of permanent deformation increases, which, ceteris paribus, leads to more significant hardening both in degree and in the depth of the hardened metal layer.

The shock vibratory rolling mode is determined by the following parameters: the force P of the shock indentation of the tool (balls, spherical strikers), the workpiece rotation frequency, the supply of the deforming tool s, the number of double strokes of the deforming element and its diameter. By varying the values ​​of these parameters, it is possible to create various systems of recesses, differing in their number per unit area of ​​the surface to be treated, the area occupied by the recesses relative to the nominal, the shape and depth of the recesses, and their relative position. Thus, by controlling the formation of recesses, it is possible to create systems with non-touching, partially overlapping holes and one-sided dynamic effects on the workpiece and machine elements, which limits the possibility of its use for processing low-rigidity and unequal rigidity parts, leads to a decrease in rigidity of machines, and the appearance of noise.

PPD with diamond tools gives good results when processing almost all metals. An exception is titanium parts. The radial force exerts the greatest influence on the roughness of the hardened surface, as during the run-in. The optimal value of this effort depends on the mechanical properties of the metal, on the shape and size of the tool and other process parameters. To calculate the optimal value of the radial force, Chekin G.I. the formula is obtained:

${\displaystyle P=k{H}_D\left(\frac{D{R}_C}{D+R_C}\right)}${\ displaystyle P = kH_ {D} \ left ({\ frac {DR_ {C}} {D + R_ {C}}} \ right)}  

where k is the coefficient determined empirically, k = 0.0013 for hardened steels and h = 0.008 for

non-hardened steels, H - hardness of the treated surface in N / mm2; D - diameter of the processed

products; RC is the radius of the sphere of the working surface of the tool.

The RPD with diamond tools is characterized by relatively small values ​​of the force P, which in the general case are in the range from 50 to 300 N. An important parameter of the smoothing process is the feed, which is usually taken in the range from 0, 005 to 0.10 mm / rev. The smoothing speed practically does not affect the microrelief of the hardened surface. However, at high speeds, vibrations can occur that degrade the quality of the work and reduce the tool life.

• Plastic deformation of metals and alloys.
• Diamond smoothing of the surface layer of machine parts and the choice of the optimal smoothing mode

• Smoothing modes. The effectiveness of the application.

• Research and optimization of diamond smoothing technology for stainless steel parts for aircraft engines and assemblies.

• Survey of Finishing Hardening Studies by Surface Plastic Deformation

• Schneider Yu.G. The operational properties of parts with regular microrelief.

1. L.G. Odintsov. Hardening and finishing of parts by surface plastic deformation. Handbook., M.: Mechanical Engineering, 1987, 328 p.
2. Shock vibrational rolling V. B. Sakhov, Yu. P. Lebedev, O. A. Parmanin, O. I. Sokolov - In: Applied mechanics c. instrument engineering. L .: L 1976
3. Schneider Yu. G. Formation of regular microreliefs on details and their operational properties. L .: Engineering, 1972.230 p.