Liburdi Turbine Services Incorporated

Dundas, Canada

Liburdi Turbine Services Incorporated

Dundas, Canada
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Henhoeffer T.,Liburdi Turbine Services Incorporated | Huang X.,Carleton University | Yandt S.,NRC Institute for Aerospace Research | Au P.,NRC Institute for Aerospace Research
Journal of Engineering for Gas Turbines and Power | Year: 2011

With the increasing utilization of braze repair in the gas turbine industry, the properties of braze joints under simulated service conditions become vital in selecting braze repair over other processes. While braze repair has often been claimed to deliver mechanical properties equivalent to that of the parent material, this is largely based on the results of tensile or accelerated creep tests for most gas turbine hot section components failure occurs as a result of thermal fatigue or thermomechanical fatigue. The damage that occurs under such conditions cannot be assessed from tensile or creep testing. This study was undertaken to characterize the fatigue properties of narrow and wide gap brazed X-40 cobalt-based superalloy and compare these properties to that of the X-40 parent material. Butt joint narrow gap and wide gap specimens were vacuum brazed using BNi-9 braze alloy. X-40 and IN-738 were used as additive materials in wide gap braze joints. To characterize the fatigue properties of the braze joints and parent material, isothermal fatigue tests were conducted at 950°C and under load control using a fully reversed sinusoidal wave form having stress amplitude of 75% of the yield strength of the parent material. The braze specimens were fatigue tested in the as-brazed condition. The fatigue test results showed that the fatigue lives of the brazed specimens were lower than that of the parent material, particularly for the narrow gap samples and wide gap samples containing IN-738 additive alloy. All fatigue failures in the brazed samples occurred in the braze joints. An analysis of the fracture surfaces using a scanning electron microscope revealed that porosity was the major contributing factor to fatigue failures in the wide gap braze joints. The testing life debit observed in the narrow gap braze samples can be attributed to the presence of brittle boride phases in the braze joint. This study also included examination of techniques for reducing the aforementioned porosity and presence of brittle intermetallic phases. © 2011 American Society of Mechanical Engineers.


Henhoeffer T.,Liburdi Turbine Services Inc. | Huang X.,Carleton University | Yandt S.,NRC Institute for Aerospace Research | Au P.,NRC Institute for Aerospace Research
Proceedings of the ASME Turbo Expo | Year: 2010

With the increasing utilization of braze repair in the gas turbine industry, the properties of braze joints under simulated service conditions become vital in selecting braze repair over other processes. While braze repair has often been claimed to deliver mechanical properties equivalent to that of the parent material; this is largely based on the results of tensile or accelerated creep tests. For most gas turbine hot section components failure occurs as a result of thermal fatigue or thermomechanical fatigue. The damage that occurs under such conditions cannot be assessed from tensile or creep testing. This study was undertaken to characterize the fatigue properties of narrow and wide gap brazed X-40 cobalt-based superalloy and compare these properties to that of the X-40 parent material. Butt joint narrow gap and wide gap specimens were vacuum brazed using BNi-9 braze alloy. X-40 and IN-738 were used as additive materials in wide gap braze joints. To characterize the fatigue properties of the braze joints and parent material, isothermal fatigue tests were conducted at 950°C and under load control using a fully reversed sinusoidal wave form having stress amplitude of 75% of the yield strength of the parent material. The braze specimens were fatigue tested in the as-brazed condition. The fatigue test results showed the fatigue lives of the brazed specimens were lower than that of the parent material, particularly for the narrow gap samples and wide gap samples containing IN-738 additive alloy. All fatigue failures in the brazed samples occurred in the braze joints. Analysis of the fracture surfaces using SEM revealed that porosity was the major contributing factor to fatigue failures in the wide gap braze joints. The testing life debit observed in the narrow gap braze samples can be attributed to the presence of brittle boride phases in the braze joint. This study also included examination of techniques for reducing the aforementioned porosity and presence of brittle intermetallic phases. Copyright © 2010 by ASME and National Research Council of Canada.


Nagy D.R.,Liburdi Turbine Services Inc. | Kuipers J.H.,Liburdi Turbine Services Inc.
Proceedings of the ASME Turbo Expo | Year: 2012

A case study is presented in which a destructive metallurgical analysis was performed on three GE Frame 7FA+e stage 1 buckets which had each been repaired using different approaches. The metallurgical condition and extent of the prior repairs are presented for each of the buckets following one additional service interval. The analyses included evaluation of the macroscopic condition, base alloy microstructure, stress rupture properties, internal and external surface coating conditions and the tip integrity. The first bucket had not been dimensionally restored at the tip during repair (i.e. the tip was still comprised of the original casting). The bucket exhibited moderate oxidation and loss of tip material. Base alloy degradation was observed at the mid airfoil height in the form of coarsening, rounding and agglomeration of the primary gamma prime precipitates. Secondary gamma prime precipitates remained in some of these regions, indicative that the alloy microstructure had not been rejuvenated by full solution treatment during repair. The second bucket had been weld repaired at the tip using a solid solution strengthened weld filler alloy. Following service, the tip exhibited significant oxidation and approximately 6mm of material loss at the mid-chord and trailing edge tip. Within the tip repair material, micro-cracks and creep voids were observed. The base alloy condition appeared similar to the first bucket. The third bucket had been tip weld repaired using a precipitation hardened weld filler alloy and rejuvenated with a full solution treatment. Following service, the bucket exhibited negligible oxidation and material loss at the tip. Overall, microstructural base alloy degradation was found to be minor. Copyright © 2012 by ASME.


Gontcharov A.,Liburdi Turbine Services Inc. | Liburdi J.,Liburdi Turbine Services Inc. | Lowden P.,Liburdi Turbine Services Inc. | Nagy D.,Liburdi Turbine Services Inc. | Patel N.,Liburdi Turbine Services Inc.
Proceedings of the ASME Turbo Expo | Year: 2014

The properties of laser, microplasma and GTAW welds on representative gas turbine blade materials are disclosed. Proprietary filler materials and technology were used to clad multipass welds onto IN738, RenéN5 and CMSX4 alloys which were then subject to vacuum heat treatment before testing. It was found that welds with a bulk content of boron up to 0.6 wt. % demonstrated a capability to heal cracks adjacent to the fusion line (HAZ cracks) and they exhibited superior tensile and stress-rupture properties at a temperature of 982°C. Welds that comprised 1.5 to 2% silicon had superior oxidation resistance at a temperature of 995°C. Combined alloying of welds with moderate amount of boron and silicon produced a unique combination of both high mechanical and oxidation properties. Healing of HAZ cracks took place during post weld heat treatment at a temperature exceeding the solidus temperature of the weld metal eutectics but below of a solidus temperature of the base material. It was found that boron and silicon additives reduced welding pool solidification temperature and increased the solidus - liquidus range. At this temperature a partial remelt of eutectics occurred allowing healing of HAZ and weld solidification cracks while weld geometry was supported by a continuous framework of high temperature dendrites. This allows the tip repair of turbine blades manufactured of precipitation strengthened superalloys that are normally prone to weld cracking. Copyright © 2014 by ASME.


Canteenwalla P.,Liburdi Turbine Services LLC | Ingistov S.,BP Watson Cogeneration | Nagy D.,Liburdi Turbine Services LLC
Proceedings of the ASME Turbo Expo | Year: 2010

Combining metallurgical analysis with performance analysis is a powerful tool for engine health monitoring and can aid in determining the root cause of component failure. A case study is presented for an industrial gas turbine engine operating at BP Watson Cogeneration Company in Carson, California where accelerated material aging and coating depletion were found in the first-stage turbine buckets after an engine up-rate to an increased firing temperature. After the material degradation was discovered, the engine was intended to be derated back to its original firing temperature, however, the performance analysis found the engine was still operating in a higher firing condition which would have continued to cause accelerated damage to the turbine buckets if not detected. Through combined analysis efforts, the error was found and corrected before the units failed from overheating. © 2010 by ASME.

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