| Benefits of the no-wax process are improved material consistency and reliability due to the reduction of: |
|
| a. |
Carbon control problems |
| b. |
Porosity |
| c. |
Shrinkage variations |
|
 |
| WAX PROCESS |
| PROS |
|
| Carbide producers have been adding organic waxes and binders to carbide powders to improve the strength of the powder compact. This facilitates easier machining and reduces the chances for machining problems. Waxes do not improve the quality of the carbide material. |
|
CONS
|
|
| 1. Excess carbon or “free carbon” porosity in the sintered part |
| The introduction of organic waxes increases the chances for carbon control problems. Free carbon softens the carbide and reduces the wear resistance of the material. |
|
| 2. Carbon deficiency |
| If too much carbon is removed during sintering, a brittle, secondary carbide phase known as eta-phase is created. Eta-phase can cause chipping, cracking or catastrophic failure. |
|
| 3. Porosity |
| Porosity has a dramatic negative effect on the breaking strength of the sintered part. Material with residual porosity will have a lower transverse rupture strength (TRS) for a given carbide grade. Porosity can lead to premature wear, chipping, cracking and catastrophic failure. |
|
| 4. Size variation |
| The presence of wax must be accounted for when considering the final shape of the sintered part. Because of the excess volume that the wax occupies in the powder compact, the chances for size variation due to distortion are increased. |
|
|
| NO-WAX PROCESS |
| PROS |
|
| With the no-wax process there are no additional variables that can affect the carbon balance within the sintered part. This means that the chances for carbon balance problems are significantly reduced. |
|
CONS
|
|
| There are no negative effects to the no-wax process during sintering. |
|
|
| HIP PROCESSING (HIPPING) |
| Wax Process |
|
| PROS |
|
| There are no beneifts of wax in carbide powders during the hipping process. In fact, wax is partially responsible for adding this pressure-sintered step. |
|
CONS
|
|
| Because wax is used, many companies require hipping to remove residual porosity left by the removal of the wax during the sintering process. This pressure sintering forces liquid cobalt into the pores created by the removal of the wax binder. |
|
| No-Wax Process |
|
| PROS |
|
| Because wax is not used, the need to add the additional hipping process is reduced. If the carbide powder is properly milled during production and properly sintered, the benefits of hipping are negligible. Hipping should be used to guarantee the quality of the carbide, not to remove flaws in the carbide created by the production process. |
|
| CONS |
|
| There are no negative aspects of the no-wax process on the hipping of carbide. |
|
|
|
 |
 |
| SUMMARY |
| With the no-wax process, the chances for production errors that lead to the formation of free carbon, eta-phase and porosity are reduced. The material will have consistent properties that you can depend on from one order to the next. The consistency of the material properties such as hardness, TRS and wear resistance will conform to your specifications. If you require consistent material quality with dependable properties, superior strength and the capability to achieve a high-quality polished finish, you should rely on carbide preforms made with the no-wax process. |
|
|
