Diamond paste

A diamond paste to be used for treating surfaces of workpieces comprising diamond powder in a mechanical mixture with surface-active and lubricating (cooling) components. The components of the paste are used in the following quantities (in % by weight): PA1 diamond powder filler: 30-2 PA2 green silicon carbide: up to 38 PA2 aerosil: up to 5 PA1 surface-active substance PA2 stearine: 20-5 PA1 low-molecular weight heat-resistant synthetic rubber: 20-40 PA1 lubricating cooling substance PA2 castor oil: 15-5 PA2 vaseline: 15-5

The invention relates to grinding and polishing compositions and may be 
used in the final finishing of surfaces of workpieces made of various 
materials, especially in the manufacture of components where elevated 
temperatures (above 100.degree. C.) are developed in the working zone 
during the lapping (polishing) of such components. 
More particularly, the invention relates to a diamond paste to be used for 
treating the surface of workpieces. 
Known in the art are diamond pastes having the following composition: 
1. diamond powder 
boron carbide 
oleic acid 
stearine 
organosilicon liquid 
2. diamond powder 
abrasive filler 
industrial oil 
oleic acid 
stearine 
(see USSR Inventor's Certificate No. 213999). 
The paste made according to the first-mentioned formulation (USSR 
Application No. 1714475/23-4 of Nov. 16, 1971) is heat resistant at a 
temperature of the surface being treated up to 85.degree.-90.degree. C. 
When used for treating the surface of workpieces at a temperature above 
90.degree. C., the viscosity of the paste considerably decreases resulting 
in a reduced productivity and impaired quality of treatment. In addition, 
boron carbide included in the composition of the paste is sensitive to 
abrupt temperature changes and oxidized at elevated temperatures which 
results in the decarbonization thereof (cf. T. M. Ippolitov, Diamond 
Abrasive Treatment, Moscow, Mashinostroenie Publishers, 1962). 
As regards the grading of boron carbide, the boron carbide powder is 
commercially available having a grading coarser than M28 so that diamond 
pastes filled with boron carbide cannot be produced with a grading finer 
than 28/20. 
The diamond paste manufactured according to USSR Inventor's Certificate No. 
213 999 contains a considerable amount of liquid components (up to 60%) 
having a low viscosity and stearine (melting point 50.degree.-60.degree. 
C.). This results in a rapid stratification and liquiefaction thereof at 
low temperatures (40.degree.-45.degree. C.), increased losses of the 
abrasive component, and finally, impaired performance and quality of 
treatment. When used for treating surfaces at a temperature above 
100.degree. C., the paste completely leaks out of the treatment zone.

It is an object of the invention to provide a diamond paste having an 
elevated heat resistance as compared to the prior-art pastes used for 
similar purpose. 
Another object of the invention is to provide a diamond paste featuring a 
predetermined viscosity which remains constant during the employment of 
the paste for lapping, grinding and finishing of the surface of 
workpieces. 
Among other objects of the invention there is the provision of a diamond 
paste having a composition eliminating unproductive losses of the abrasive 
component and improving the quality of treatment of the surfaces of 
workpieces. 
These and other objects are accomplished by the provision of a diamond 
paste to be used for treating the surfaces of workpieces, comprising 
diamond powder in a homogeneous mechanical mixture with surface-active and 
lubricating cooling components, which is characterized in that the 
lubricating cooling component comprises a low-molecular weight 
heat-resistant synthetic rubber used in an amount of at least 1/5 by 
weight of the paste. 
It is the presence of synthetic rubber in the composition of the diamond 
paste that provides for an improved heat resistance of the paste and 
maintenance of a predetermined viscosity of the mass thereof. 
In accordance with one embodiment of the invention, the diamond paste is 
characterized in that with a filler included in the composition thereof, 
the filler comprises an organo-silicon compound - aerosil. 
This contributes to still more improved properties of the diamond paste to 
be used for the above-mentioned purposes. 
And finally, in accordance with another embodiment of the invention, the 
diamond paste is characterized in that it has the following composition 
(in % by weight): 
diamond powder filler: 30-2 
green silicon carbide: up to 38 
aerosil: up to 5 
surface-active substance--stearine: 20-5 
low-molecular weight heat-resistant synthetic rubber: 20-40 
lubricating cooling substance 
castor oil: 15-5 
vaseline: 15-5 
The above-mentioned precise composition of the diamond paste according to 
the invention has experimentally proved to exhibit a high performance as 
regards both the heat resistance of the paste composition and quality and 
productivity of treatment of the surface of workpieces. 
The invention will now be described in detail with reference to a specific 
embodiment thereof illustrated by an example of the production technique 
for preparing the diamond paste, as well as one of the precise 
compositions thereof which was studied experimentally. 
Depending on the proportioning of certain components and type of a diluent 
used, the diamond paste according to the invention may be used for 
treating surfaces whose temperature varies over the range from 140.degree. 
to 200.degree. C. (and even up to 350.degree. C.) without any critical 
changes in the viscosity. This is ensured due to a combination of a 
low-molecular weight heat-resistant synthetic rubber, aerosil, vaseline 
and castor oil. A conventional viscosity of low-molecular weight 
heat-resistant synthetic rubber is 601-1080 S, heat resistance is 2.0. The 
use of vaseline and castor oil makes it possible to obtain the paste 
having a required lubricating capacity, while the viscosity of castor oil 
remains unchanged under heating. Stearine is used as surfactant. 
The production technique for preparing the paste comprises the following 
steps: 
(1) castor oil is poured into a vessel containing an appropriate quantity 
of rubber, then vaseline is added, and the mixture is thoroughly stirred 
to obtain a homogeneous viscous white mass (mixuture 1); 
(2) diamond powder and abrasive filler are poured into mixture 1, and the 
mass is stirred for 15-20 minutes at room temperature (mixture 2); 
(3) aerosil is gradually added to mixture 2, and the mass is again 
thoroughly stirred (mixture 3); 
(4) stearine is heated at 40.degree.-50.degree. C. and is poured into 
mixture 3, whereafter the paste is stirred at room temperature to obtain a 
mass with daimond grains uniformly distributed within the entire volume 
thereof. 
Positive results have been obtained in testing the paste of the following 
composition (in % by weight): 
diamond powder: 10% 
low-molecular weight heat-resistant synthetic rubber: 40% 
stearine: 20% 
vaseline: 15% 
castor oil: 10% 
aerosil: 5% 
When tested, the diamond paste having the above-given composition exhibited 
heat resistance which was considerably better than that of the prior art 
pastes; moreover, it has been found that the viscosity of the new paste 
remained at a predetermined level during a long-term use for mechanical 
abrasive treatment of the surface of workpieces, while unproductive losses 
of the abrasive component-diamond powder were reduced, and high quality of 
the workpiece surface after the treatment was achieved even at 
comparatively high temperatures at which prior art pastes were 
substantially unsuitable and inefficient. 
It should be noted that while only one of possible precise compositions of 
the diamond paste was cited hereabove, the tests have been conducted with 
different contents of the above-mentioned components of the paste; thus, 
diamond powder was used in an amount from 2 to 30% by weight, green 
silicon carbide from a tiny fraction to 38% by weight, aerosil up to 5% by 
weight, stearine from 5 to 20% by weight, low-molecular weight 
heat-resistant synthetic rubber from 20 to 40% by weight, and castor oil 
and vaseline from 5 to 15% by weight, respectively. 
Even with such variable contents of the components it has been revealed 
that the positive properties of the diamond paste according to the 
invention remained unchanged.