The characteristics of abrasive tools (the type of grinding wheel, granulation of the super hard grain, type of structure, hardness, and the type of binder) contain information on the type of supporting body materials used (e.g., dural, ceramic, steel). In this work, diamond wheels were obtained on ceramic supporting bodies, containing a sintered mixture of white alumina 99A granulation F320, green silicon carbide 99A granulation F320, and binder Ba23 bis, together with modifiers. The mechanical properties (hardness, bending strength) of ceramic supporting bodies were tested. The structure of the phase boundary of the ceramic supporting body–abrasive grinding tool was analyzed on a BEC (backscattered electron composition) image by using SEM (Scanning Electron Microscopy). It was found that the hardness of the supporting body was slightly lower (70–75 HRB) than the diamond wheels (76–81 HRB). The bending strength of the supporting bodies was high (85 ±2 MPa). The BEC image from the scanning microscope did not show a sharp transition between the ceramic supporting body and the grinding wheel. Preliminary operational tests showed significant improvement in grinding wheel efficiency in comparison to diamond tools with the same ceramic binder on a duralumin supporting body during machining of G30 sintered carbide bush.
New materials used in industry, such as plastics reinforced with glass fiber composites, non-ferrous metal alloys reinforced with hard particles, composites made of sintered carbides doped with super-hard grains, and super alloys of nickel (Hastalloy, Waspalloy, Inconel 718, Udimet 720) and titanium (Ti6Al4V, TiAl) for precise and effective machining of cavities, require novel machining technologies as well as novel tools, like super-hard abrasive tools with new binders and supporting bodies (
For the proper choice of grinding tool for a specific application, the characteristics of the tool should be composed from not only the description of the binder and abrasive grain type and concentration, but it also should include information on the type of supporting body to which the abrasive coating of the tool has been attached. The literature analysis of the manufacturing catalogue (
As a result, it is necessary to adapt the tool body to the type of machining operation and the type of adhesive used. The aim of our work is to obtain a diamond abrasive tool with a ceramic bond and ceramic supporting body in one technological operation. The body of the diamond tool contains a newly developed ceramic bond modified with green silicon carbide and white fused corundum in appropriate proportions. The advantage of using such a supporting body is the limitation of possibility of residual stresses appearing at the interface between the supporting body and the abrasive ring, with similar hardness and bending strength.
The subject of research was abrasive composites with structures of 40 and 42 containing a working ring with diamond grains and a ceramic bond Ba23 bis (
After the heat treatment, the tools were subjected to a sensory analysis (measurement of diameter, height of the coating, determination of deviations from the assumed values). Next, the tools were examined using a JOEL JSM 6460LV scanning electron microscope. The measurements were made in high vacuum conditions (10−5 Torr), at accelerating voltage of 20 kV and 100× magnification, using a backscattered electron composition (BEC) image. Microanalysis of the chemical composition “along the line” at the border of the body of the ceramic abrasive coating was made, along with maps of the surface distribution of the elements in the same area, using the EDS INCA X-act Energy 350 spectrometer by Oxford Instruments. The hardness of the grinding wheel was measured along the entire diameter of the wheel, based on the reading of a 1/16-inch steel ball indentation on the HRB scale on the Rockwell hardness tester. The bending strength of the body abrasives was tested using a three-point bending method on a 50 × 4 × 4 × 4 mm Instron machine under the following conditions: support spacing of 40 mm, test rate of 0.1 mm/min, and 90% Fmax failure rate. Preliminary and comparative tests were carried out on diamond grinding wheels with a ceramic bond with a ceramic supporting body (2 pieces) and diamond grinding wheels with the same adhesive bond bonded to a duralumin supporting body (2 pieces).
Sensory analysis of the diamond grinding wheels with ceramic bodies type 1A1 35x5x5x5x10 D 126 c100 V (four pieces) showed deviations in tool diameter in the range of 0.12% (0.04 mm—average from four measurements) and on the height of the coating—shrinkage of 0.09 mm, i.e., 1.8%—which confirmed the proper selection of heat treatment characteristics (
The analysis of the ceramic coated grinding wheel surface in the BEC (backscattered electron composition) image did not show any distinctive marked difference between the ceramic supporting body and the grinding wheel coating (
On the other hand, the content of the aluminum significantly increased on the surface of the ceramic supporting body. Silicon was present both in the grinding wheel coating and in the ceramic supporting body. This was confirmed by maps of the surface distribution of the elements of this area (
The results of the tests of the hardness of the grinding wheels with structures of 40 and 42 showed slight differences in values along the line of the ceramic body diamond mound. For both structures, the average value of the hardness of the body was in the range 70–75 HRB and the hardness of the diamond ring 76–81 HRB (
The tests were carried out on an SOJ hole grinder made by Jotes (
In
The analysis of the obtained results (hardness, bending strength) confirmed the proper selection of the chemical composition of the ceramic supporting body for a diamond grinding wheel with a ceramic binder, as well as the characteristics of heat treatment (curing time and controlled cooling).
The BEC image from the scanning microscope did not show any sharp borderline between the ceramic body and the grinding wheel coating (
Operational tests of the grinding wheels when grinding holes in G30 sintered carbide sleeves showed the significant influence of the type of applied bodies on the tool performance.
The possibility of shortening the grinding wheel production time by sticking the grinding wheel coating to the duralumin supporting body reduces the cost of manufacturing the tool and, most of all, affects its quality and durability.
The concept of using this modified bond for abrasive tool bodies is limited to small size grinding tools (ϕ 12–50 mm) because of the slightly higher cost of manufacturing glass frit than PA6 duralumina supporting body. This kind of grinding tool can be used for grinding internal and external cylindrical surfaces e.g., in rolling bearing elements, carbide matrix elements, and holes in ceramic nozzles.
Conceptualization, B.S.-B.; Methodology, B.S.-B. and M.K.; Validation, B.S.-B., M.K. and P.F.; Formal Analysis: B.S.-B., P.F., and M.K.; Investigation, B.S.-B., P.F., G.S. and M.K.; Resources, B.S.-B.; M.K., Data Curation, B.S.-B.; Writing—Original Draft Preparation, B.S.-B.; Writing—Review and Editing, B.S.-B.; Visualization, B.S.-B., G.S., and P.F., Supervision, B.S.-B.; Project Administration, B.S.-B.; Funding Acquisition, B.S.-B.
The project was carried out at Łukasiewicz – IAMT own funds.
The authors declare no conflict of interest.
Diamond grinding wheels with ceramic body (
Micrograph of the surface area of the boundary area ceramic supporting body—diamond grain (obtained by backscattered electron composition (BEC) techniques)
SEM image of wheel surface (
Relative comparison of properties of materials used for grinding wheel bodies (
Material | Designation | Vibration Damping | Thermal Conductivity | Mechanical Strength |
---|---|---|---|---|
sintered alumina | I | x x x | x x x | x x x |
duralumin | A | x x | x x x x | x x x x |
bakelite | B | x x x x | x | x x |
steel | J | x | x x x x | x x x x |
ceramic abrasive sinter | K | x x x | x x x | x x x |
x—Less pronounced of property; x x x—Well pronounced of property.
Results of mechanical properties tests of ceramic supporting bodies
Designation | Average Supporting Body Hardness |
Average Ceramic Diamond Ring Hardness |
Average Bending Strength of the Body |
---|---|---|---|
1A135x5x5x5x10D76EA+SZ s.40 | 72.5 ±2 | 77 ±2 | 84 ±2 |
1A135x5x5x5x10D76EA+SZ s.40 | 74.0 ±1 | 78 ±2 | 86 ±2 |
1A135x5x5x5x10D76EA+SZ s.42 | 73.0 ±2 | 79 ±2 | 84 ±2 |
1A135x5x5x5x10D76EA+SZ s.42 | 72.5 ±2 | 77 ±1 | 85 ±1 |
1A1 type of wheels shape (peripheral shape); 35x5x5x5x10—wheels dimensions; D76—granulation of diamond grain; EA+SZ s.40—type of modification.
Test parameters
Parameter | Value |
---|---|
Wheel circumferential velocity | 18.22 m/s |
Work piece peripheral speed | 250 rpm |
Longitudinal displacement speed | 5 m/min |
Grinding depth in single pass | 0.01 mm |
Cooling | flooding method (GRINDIX coolant) |
Results of exploitation tests of grinding wheels
Designation | Circumferential Speed of Grinding Wheel |
Loss on Grinding Wheel Diameter R |
Relative Wear |
---|---|---|---|
1A1 35x5x5x10 D76, EA+SZ 100 V | 18.00 | −0.01 ±0.002 | 1.570 |
1A1 35x5x5x10 D76, EA+SZ 100 V | 22.00 | −0.02 ±0.002 | 2.873 |
1A1 35x5x5x10 D76, 100 V | 18.00 | −0.015 ±0.003 | 2.156 |
1A1 35x5x5x10, D76, 100 V | 22.00 | −0.025 ±0.003 | 3.594 |