Systematic investigation of failure analysis on a steam trap bypass tube in a coalfired power plant

A steam trap bypass tube in a power plant was totally fractured. The aim of this study is to examine the evidence presented by the steam trap bypass tube failure, determining the failure mechanism, determining the root cause of the failure and to recommend appropriate corrective actions. The power plant is a coal fired power plant with its normal operation temperature of 540°C. This study consists of failure mode inventory collection of the steam trap bypass tube failure, collection of background information about the process, component function and operating conditions. Detailed investigation carried out by visual examination, nondestructive testing (NDT), metallurgical testing which consists of microstructure examination, chemical testing and mechanical testing. Optical Microscopy (OM), Scanning Electron Microscopy (SEM) combined with Energy Dispersive X-ray Spectroscopy (EDS), Glow Discharge Spectrometer (GDS) and Energy Dispersive X-ray Diffraction (XRD) experiments were used throughout the investigation on the sample obtained. From the evidence with considering the contribution factors such as temperature, pressure and environment, a fault analysis was made and it can be concluded that the cause of failure to the steam trap bypass is due to multi causes which consists of creep failure and hydrogen damage. The root cause of high temperature creep and hydrogen damage which occurred at the steam trap bypass tube is due to material properties that are inadequate for the actual operating conditions of a steam trap bypass tube which is not according to the specification. The material must be actually ASTM SA-335-P22 (2.25Cr-lMo) with 490MPa minimum tensile strength and 320MPa minimum yield strength. However from the investigation found that the material used was ASTM SA-l92 (low strength carbon steel) with 324MPa minimum tensile strength and 180MPa minimum yield strength

Effectiveness of dimple microtextured copper substrate on performance of Sn-0.7Cu solder alloy

This paper elucidates the influence of dimple-microtextured copper substrate on the performance of Sn-0.7Cu solder alloy. A dimple with a diameter of 50 µm was produced by varying the dimple depth using different laser scanning repetitions, while the dimple spacing was fixed for each sample at 100 µm. The dimple-microtextured copper substrate was joined with Sn-0.7Cu solder alloy using the reflow soldering process. The solder joints’ wettability, microstructure, and growth of its intermetallic compound (IMC) layer were analysed to determine the influence of the dimple-microtextured copper substrate on the performance of the Sn-0.7Cu solder alloy. It was observed that increasing laser scan repetitions increased the dimples’ depth, resulting in higher surface roughness. In terms of soldering performance, it was seen that the solder joints’ average contact angle decreased with increasing dimple depth, while the average IMC thickness increased as the dimple depth increased. The copper element was more evenly distributed for the dimple-micro-textured copper substrate than its non-textured counterpart

ZINC MICRO-ALLOYING ADDITIONS IN Sn-0.7Cu LEAD-FREE SOLDER ALLOYS. SHORT REVIEW

Sn-Pb solder alloy has been replaced with lead-free solder alloys due to the negative effect for environment and human health. The additions of Zinc (Zn) micro-alloying element in Sn0.7Cu lead-free solder alloy were reported by several researchers in improving the performance of Sn-0.7Cu solder alloy. This paper reviews the research findings available on the additions of zinc micro-alloying in Sn-0.7Cu solder alloy. It can be concluded that zinc micro-alloying additions were reported to improve the mechanical properties, phase aanalysis and microstructure of the solder free solder joint

EFFECT OF BISMUTH CONTENT ON MICROSTRUCTURE, MELTING TEMPERATURE AND UNDERCOOLING OF SN-0.7CU SOLDER ALLOY

The aim of this manuscript to study the influence of Bismuth (Bi) addition on the microstructure, melting temperature and undercooling of Sn-0.7Cu solder alloys. In this study, several Bi composition were chosen which is 0 wt.%, 0.25 wt.%, 0.5 wt.%, 1.0 wt.% and 2.0 wt%. The result indicated that with addition of Bi element, it can refine the β-Sn and reduce the size of primary Cu6Sn5. The melting temperature of Sn-0.7Cu solder alloy was observed by DSC result and found there is no significant changes of melting temperature by Bi additions. However, with Bi addition, it will reduce the undercooling of the Sn-0.7Cu solder alloys