Case Study: In-Situ Linear Reciprocating High-Pressure Tribometry Testing
Overview
Tribology—the science of friction, wear, and lubrication—is fundamental to the performance and durability of mechanical systems that involve sliding contact. In situ linear reciprocating high-pressure tribometry enables real-time measurement of friction coefficient and wear rate under controlled contact pressures, sliding velocities, temperatures, and lubrication conditions that closely replicate the most demanding industrial service environments.
This case study explores how in situ tribometry testing was applied to solve a critical wear problem in a high-pressure industrial sealing application within the oil and gas sector.
The Engineering Challenge
A manufacturer of high-pressure reciprocating compressor seals was experiencing premature wear failure of PTFE-based seal rings operating in a high-pressure natural gas environment at contact pressures up to 40 MPa. Seal life was significantly shorter than predicted by conventional tribological data, leading to costly unplanned maintenance shutdowns.
The challenge was to understand the friction and wear mechanisms operating at realistic contact pressures and in the presence of pressurised gas, which affects lubricant film formation and material behaviour differently from ambient conditions.
Test Configuration
The tribometry test was configured as follows:
- Test geometry: Pin-on-flat linear reciprocating configuration
- Contact pressure: 5–40 MPa (incremental)
- Stroke length: 20 mm
- Sliding speed: 0.1–0.5 m/s
- Temperature: 25–80°C
- Environment: High-pressure nitrogen (simulating natural gas), up to 35 MPa
- Specimen: PTFE-composite seal material vs. hardened steel counterface
In situ friction coefficient was continuously recorded. Post-test wear volume was measured using non-contact profilometry.
Results and Analysis
At contact pressures below 20 MPa, the friction coefficient remained stable at approximately 0.08–0.12, consistent with the lubricious behaviour of PTFE. Above 25 MPa, friction increased sharply to 0.25–0.35, coinciding with a dramatic increase in specific wear rate.
SEM analysis of worn surfaces revealed that at high contact pressures in the pressurised gas environment, the PTFE transfer film—normally a thin, adherent lubricating layer on the steel counterface—was disrupted and became discontinuous. This led to direct PTFE-steel contact and accelerated adhesive and abrasive wear mechanisms.
Root Cause and Solution
The root cause was identified as pressure-induced disruption of the PTFE transfer film. The solution involved:
- Replacing neat PTFE with a PTFE/bronze/MoS₂ composite formulation providing better transfer film stability at high pressures.
- Modifying the surface finish of the steel counterface to a Ra of 0.1–0.2 µm to promote stable transfer film formation.
The reformulated seal material was retested and demonstrated a friction coefficient of 0.10–0.14 and a 75% reduction in wear rate at 40 MPa contact pressure.
Value of In Situ High-Pressure Tribometry
This case study demonstrates that tribological testing must replicate actual service conditions—including contact pressure, environment, and temperature—to generate meaningful predictive data. In situ testing eliminates the need for post-test reconstruction of friction events, providing higher data fidelity and faster root cause identification.
Why Choose Infinita Lab for Tribometry Testing?
Infinita Lab offers comprehensive in situ tribometry testing services, including linear reciprocating, rotating, and fretting configurations, across its network of specialised accredited laboratories. Our project management expertise ensures your testing program delivers actionable results efficiently.
Looking for a trusted partner to achieve your research goals? Schedule a meeting with us, send us a request, or call us at (888) 878-3090 to learn more about our services and how we can support you. Request a Quote
Frequently Asked Questions (FAQs)
What is linear reciprocating tribometry? Linear reciprocating tribometry measures friction and wear when two surfaces slide back and forth against each other in a straight line. It simulates the contact mechanics of seals, pistons, guide rails, and other reciprocating machine elements.
Why is "in situ" testing important in tribology? In situ testing measures friction coefficient and wear in real time during the test, rather than only measuring post-test wear volume. This captures transient behaviour, running-in phenomena, and the onset of failure modes that would be missed by post-test analysis alone.
What contact pressure range can be tested? Modern high-pressure tribometers can test from less than 1 MPa to over 3 GPa contact pressure, depending on the contact geometry and specimen size.
Can tribometry be performed in liquid lubricants or gas environments? Yes. Environmental cells allow testing in oils, greases, water, and high-pressure gases (N₂, CO₂, H₂, natural gas). Environmental fidelity is critical for accurate prediction of service behavior.
What surface analysis techniques complement tribometry? Post-test analysis commonly includes SEM/EDS of worn surfaces, non-contact profilometry for wear volume measurement, Raman spectroscopy for carbon film characterization, and XPS for surface chemistry analysis.
