Failure analysis of a commercially pure titanium tube in an air conditioner condenser

Purpose The purpose of this paper is to determine the failure reasons and failure mechanism of the commercially pure titanium air conditioning condenser. Design/methodology/approach In this paper, chemical analysis, metallographic observation, visual examination and scanning electron microscope examination, corrosion products analysis and working conditions analysis were adopted for determining the reasons for the failure of the condenser. Findings The results indicated that TA2 titanium pipe perforation failure is caused by the synergistic effect of crevice corrosion and deposit corrosion. The corrosion processes can be divided into three steps. Originality/value This research is an originality study on the failure case of a commercially pure titanium air conditioning condenser. This study makes up for the shortage of titanium alloy failure cases and also gives the result of the failure reason and failure mechanism for titanium, which has an engineering significance.

Analysis on the Interference Assembly of Camshaft With Knurled Tube and Cam

Interference joint is one of the most advanced assembly methods for camshaft. In this paper, the mechanism of camshaft interference assembly is analyzed by thick-wall cylinder model. Joining/tortion experiments are done to estimate the joining force and connection strength. The relationship between the torque capacity, joining force and interference of the camshaft is established by the experiment results. Joining force linear increase with the interference, and torque exponential increase with it. The plastic deformation characteristics of knurled teeth on the tube during the joining process are obtained by metallographic observation. The results reveal the metal line changes continuously of the knurled tube. The knurled tooth tip turns over after joining. And elastic limit would be reached in the extrusion region.

Step-Sintering of Fe-(1-3)%Mn-0.8%C Steels

The aim of the study was to examine how the microstructure changes during heating of Fe-Mn-C system (step-sintering). Mixtures of powders containing 1 – 3 % Mn and 0.8 % C were prepared in Turbula TC2 mixer for 30 minutes. Before step-sintering, the dilatometric investigations were carried out, which allowed to obtain phase transformation temperatures of Fe-(1-3)Mn%-0.8%C system. Following dilatometric investigations, 4 steps – temperatures were determined dependently of isothermal sintering temperature. The commonly used industry temperatures – 1120 °C and 1250 °C – were set as target temperatures. For each of them, 4 heat steps were carried out. The procedure of investigations was as follows: samples were heated to the step temperature with heating rate 60 K/min, then isothermally sintered at step temperature for 5 min, and finally cooled to the room temperature with cooling rate ~ 66 K/min. Fe-Mn-C samples were mechanically (tensile) tested. After tensile tests, metallographic observations of the samples were performed. Based on the results obtained, the tensile strength was increasing with the increasing of the step temperature. The metallographic observation showed the microstructure evolution – with increasing the step temperature, decreasing of porosity was observed.

Threaded Failure Analysis for Three-Dimensional Horizontal Wells Casing

In view of the external thread fracture during casing running in a well in Xinjiang Oilfield, the failure reasons of thread fracture were analyzed by combining the theory with experiment, and the casing safe service window with harsh working conditions was given. The operation of the failed casing and determined the actual working conditions of the casing threaded joints during the running process were investigated in this paper. According to the theoretical method, the boundary conditions and load conditions of the fracture casing joint in service were determined. With the aid of full-scale physical simulation test device, as well as the above boundary conditions and load conditions, the same batch casing tensile bearing characteristics were determined. Through nondestructive testing, the metallographic observation, scanning electron microscopy, spectral analysis and up-and-down test, the main controlling factors of casing thread fracture were determined. By the finite element analysis, the casing threads service state under axial tension and bending loads was established, the safety performance of threads under ideal working conditions was studied, and the fatigue mechanism of threads was revealed. Combined with the analysis results, the corresponding relationship between the casing tensile bearing characteristics and safety factor was given, which provides technical support for the safe service selection of casing body and thread under harsh conditions, saving cost and shortening the well construction period.

Analysis on three typical abnormal microstructures of overhead power line suspension clamps

This article lists three typical abnormal microstructures of overhead power line suspension clamps, including inclusion, flake graphite and cementite network. A series of tests including macro check, hardness measurement, composition tests, Energy-dispersive x-ray analysis and metallographic observation have been carried out. The experimental results showed that the causes of abnormal microstructures mainly include: high content of impurities, flake graphite blank and unfulfilled annealing heat treatment. It is suggested to strengthen the supervision on suspension clamps before using, and focus on the quality inspection of metallographic structure and composition.

Failure analysis of isolation switch in transformer substation

To analyze the fault cause of metal parts of isolation switch, a series of tests including macro check, penetrate testing, hardness measurement, composition tests and metallographic observation have been carried out. The experimental results showed that the failure of connecting lever was caused by improper processing, which resulted in the limitation of cracking and stress corrosion cracking. Based on this, the corresponding noteworthy key points were put forward to avoid similar accidents.

Microstructure and Mechanical Properties of Al-12Si Alloys Fabricated by Ultrasonic-Assisted Laser Metal Deposition

This paper presents a method of ultrasonic-assisted laser metal deposition of Al-12Si alloy. The effects of the ultrasonic power and remelting treatment on the development of porosity, microstructural evolution, and tensile properties of the deposits were investigated. The results suggested that a combination of an ultrasonic vibration and remelting treatment could prolong the existence of the molten pool and the effect of the ultrasound. Therefore, the density of the samples increased from 95.4% to 99.1% compared to the as-prepared samples. The ultrasonic action in the molten pool could not only increase the density of the samples but also refine the grains and improve the tensile properties of the samples. Metallographic observation showed that the maximum size of the primary α-Al dendrites were refined from 277.5 µm to 87.5 µm. The ultimate tensile strength and elongation of the remelting treatment samples with ultrasonic vibration were ~227 ± 3 MPa and 12.2% ± 1.4%, respectively, which were approximately 1.17 and 1.53 times those of the as-prepared samples, respectively. According to the tensile properties and fracture analysis, the density increase dominated the improvement of the mechanical properties.

Impact of corrosion product removal to depth of corrosion damage in weldment joint

Corrosion flaws in pipelines can caused severe financial losses and also can be dangerous for people. One of the most frequently damaged parts are dissimilar pipe welds. We would like to understand how corrosion process reacts on corrosion product removal. Outputs from experiment will be used for production of test specimens. For testing we chose standard dissimilar weldment used in Czech power plants. It is joint with 08Ch18N10T and 22K (GOST) steel. Joint is cut to 24 same specimens. There are exposed to flowing water solution of 5% NaCl. Half of the specimens are regularly mechanically cleaned. The joint is metallographically observed and parts with and without corrosion products are compared. Water salt solution increased pH from 7,25 to 7,86 during 31 days test and conductivity varies around 74 mS cm−1. Metallographic observation indicates that corrosion under corrosion products layer is locally speed up and causes pitting corrosion. Cleaned specimens indicate plane corrosion with lower depth. These results indicate that slag in pipeline could locally speed up corrosion depth penetration. On the other hand, solutions with abrasive particles (which can wipe out the corrosion product) will probably facilitate plane corrosion damage on pipeline walls. This test brings us another knowledge, how to simulate realistic corrosion damage for production of NDT qualification test pieces.

Piston Failure Analysis on Four-Wheeled 1000cc Engine Cylinder Capacity

Pistons are one of the main components of a 1000 cc engine that functions as a pressure suppressor and a recipient of pressure combustion in the combustion chamber. In the examination of the 1000 cc sedan engine that has been operating for 30,000 hours found a rough sound on the engine and experienced loss compression on the cylinder block number 2. The purpose of the study was to obtain the factors causing the deformation of the piston 1000 cc sedan vehicles. The research method used is metallographic observation using ASTM E 3 and ASTM E 112, testing hardness using ASTM E 92 and SNI 19-0409-1989 and testing chemical composition using ASTM A 751. The results of research on piston damage can be seen that observation macrostructure proves that there is plastic deformation on the surface area of the piston material, the results of microstructure observation are known to occur microcrack on the top surface of the right side of the piston, there is no change in microhardness between the piston material in the deformed area with the deformed piston material hardness, piston material made of alloy Al-Si. In the area of the piston surface that experiences deformation, Mg2Si and Mg2Al3 compounds are formed, these compounds which cause microcrack on the piston's upper surface. Plastic deformation on the piston surface occurs due to a collision between the piston surface and the cylinder head due to the buildup of crust on the piston surface.

Relationship between the Size and Inner Structure of AM Powder Particles

Additive manufacturing (AM) is today’s buzzword—and not only in commercial production. One of the AM techniques produces 3D objects with complex geometry using a laser beam. The relationship between the morphology of individual powder particles and the printing process has not been adequately documented yet. This article presents a detailed microscopic analysis of virgin and reused powder particles of maraging steel. Metallographic observation was performed using a scanning electron microscope (SEM). Detailed analyses of individual particles were carried out using SEM with a focused ion beam (FIB) milling capability. Analyses of elemental distribution and phase distribution were performed using EDS and EBSD, respectively. The findings have led to a better understanding and prediction of defects in additive-manufactured products.