GT15 Sintered vs Hot Forged
An important question – Did the turbo fail due to oil contamination – or did the thrust bearing fail causing oil contamination..?
This is a question turbo repairers need to ask when analysing warranty returns.
Over the years turbocharger designs have evolved as new technology becomes available. Materials and manufacturing processes have changed as the turbo OEM’s have had to reduce weight and learn to work with changing oil viscosities, as well as take advantage of new materials. The important issue with thrust bearings is that different materials and manufacturing processes require different designs to achieve the same result.
In the aftermarket, we often see thrust bearings, which were originally designed by the OEM as high strength silicon brass alloys using a hot forging process, being replaced by sintered powder metal with low cost tooling as it can result in lower piece part manufacturing costs.
DID YOU KNOW? The scratched surface is a controlled finish designed to aid oil retention, helping the turbo during cold start-ups.
Key Points:
- Important issue – different materials and manufacturing processes require different designs to achieve the same result;
- Powder metal (sintered) is not as strong as the original designed material;
- Thrust bearings can crack and fail in service under normal operating loads;
- The component failure causes the turbo to fail;
- Turbo repairers often diagnose this as oil contamination – poor quality part is not noticed.
Is the material strength appropriate for the application?
Effects on the Industry
This is a significant issue to the industry – but the worst part is that it is silent. When a thrust fails in this way, the resulting failure is usually misdiagnosed as oil contamination. In reality it is a failure through inappropriate use of lower strength materials. This is causing many turbo failures and warranty issues, which should not happen and this has an effect on the whole industry.
