Assessment of Microstructure and Mechanical Properties in Laser Cladding, Welding and Surface Polishing Through Online Monitoring of Thermal History

2019 ◽  
Author(s):  
Ashish Kumar Nath ◽  
Muvvala Gopinath
Keyword(s):  
Mechanical Properties ◽  
Laser Cladding ◽  
Thermal History ◽  
Thermal Stresses ◽  
Ceramic Coating ◽  
Online Monitoring ◽  
Laser Polishing ◽  
Melt Pool ◽  
On Line ◽  
Repeatability And Reproducibility

Abstract Monitoring and controlling the microstructure, phases, and thermal stresses in laser cladding of materials which determine their mechanical properties is essential for ensuring repeatability and reproducibility in refurbishing engineering parts and building functional parts by layer-by-layer deposition in additive manufacturing process. Several studies have been reported on on-line monitoring of temperature, melt-pool geometry, and porosity etc. in laser powder deposition process, but only a few on the assessment of solidification morphology, microstructure, and thermal stresses. Since these features are dictated by the melt-pool lifetime, cooling and solidification rates, their effects on the evolution of microstructure and the state of ceramic particles in laser deposition of Ni-super alloy and metal matrix composites of WC and TiC are investigated in the current study. Good correlation exists between the thermal history monitored online and the solidification characteristics. Process maps based on the melt-pool lifetime as a function of laser cladding parameters for these materials are developed. On-line monitoring of thermal cycle is extended to laser welding of stainless steel and titanium which are difficult to join together due to the formation of brittle intermetallic phases, and laser polishing of thermal sprayed ceramic coating to develop a better understanding and control of these processes. Melt-pool lifetime is found to have significant effect on the crack growth in fusion welding and by optimizing the former the later could be mitigated. Similarly, the cooling rate in laser polishing of thermal sprayed ceramic coating is found to have significant influence on the surface roughness and residual stress. These studies show that the online monitoring of thermal history can be exploited for controlling the process quality and ensuring the repeatability and reproducibility in different laser material processing modalities.

Monitoring of Molten Pool Thermal History and its Significance in Laser Cladding Process

2017 ◽  
Author(s):  
Muvvala Gopinath ◽  
Debapriya Patra Karmakar ◽  
Ashish Kumar Nath
Keyword(s):  
Mechanical Properties ◽  
Laser Cladding ◽  
Thermal History ◽  
Molten Pool ◽  
Metal Matrix ◽  
Life Time ◽  
Wear Properties ◽  
Laves Phases ◽  
Slow Cooling ◽  
Calculated Effect

The current study focuses on the process monitoring of thermal history and its significance in laser cladding technology. Thermal history of the molten pool during laser cladding was monitored using an IR-pyrometer and the molten pool life time, solidification shelf duration and cooling rates were calculated. Effect of these on three different cases was studied in brief: (a) Elemental segregation in nickel based super alloy, (b) Wettability between metal matrix and WC particles and (c) Decomposition of TiC particles in metal matrix. It was found that with slow cooling rate, formation of Laves phases in Inconel 718 became dominant which is detrimental to the mechanical properties. Also, slow cooling resulted in the decomposition of TiC particles resulting in poor wear properties of the coating. In contrast to the above two cases where slow cooling was found to be detrimental for mechanical properties of the coating, it increased wettability as well as bonding through diffusion between the WC particles and the metal matrix. Also the effect of presence of TiC and WC in metal matrix on molten pool thermal history was studied. The microstructures, elemental segregations and fractured surfaces were characterized using SEM and EDS analyses.

Modeling and Experiments of Laser Cladding With Droplet Injection

2005 ◽  
Vol 127 (9) ◽  
pp. 978-986 ◽  
Author(s):  
J. Choi ◽  
L. Han ◽  
Y. Hua
Keyword(s):  
Fluid Flow ◽  
Laser Cladding ◽  
Dynamic Motion ◽  
Cladding Layer ◽  
Melt Pool ◽  
Material Deposition ◽  
Modeling And Experiments ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
The Impact

Laser aided Directed Material Deposition (DMD) is an additive manufacturing process based on laser cladding. A full understanding of laser cladding is essential in order to achieve a steady state and robust DMD process. A two dimensional mathematical model of laser cladding with droplet injection was developed to understand the influence of fluid flow on the mixing, dilution depth, and deposition dimension, while incorporating melting, solidification, and evaporation phenomena. The fluid flow in the melt pool that is driven by thermal capillary convection and an energy balance at the liquid–vapor and the solid–liquid interface was investigated and the impact of the droplets on the melt pool shape and ripple was also studied. Dynamic motion, development of melt pool and the formation of cladding layer were simulated. The simulated results for average surface roughness were compared with the experimental data and showed a comparable trend.

scholarly journals A novel melt pool mapping technique towards the online monitoring of Directed Energy Deposition operations

2021 ◽  
Vol 53 ◽  
pp. 576-584
Author(s):  
Kandice S.B. Ribeiro ◽  
Henrique H.L. Núñez ◽  
Jason B. Jones ◽  
Peter Coates ◽  
Reginaldo T. Coelho
Keyword(s):  
Energy Deposition ◽  
Online Monitoring ◽  
Mapping Technique ◽  
Melt Pool ◽  
Directed Energy Deposition ◽  
Directed Energy

scholarly journals A Review on Microstructural Features and Mechanical Properties of Wheels/Rails Cladded by Laser Cladding

Micromachines ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 152
Author(s):  
Xinlin Wang ◽  
Lei Lei ◽  
Han Yu
Keyword(s):  
Mechanical Properties ◽  
Service Life ◽  
Process Optimization ◽  
Laser Cladding ◽  
Future Development ◽  
Heat Affected Zone ◽  
Small Deformation ◽  
Microstructural Characteristics ◽  
Low Input ◽  
Recent Developments

The service life of rails would be remarkably reduced owing to the increase of axle load, which can induce the occurrence of damages such as cracks, collapse, fat edges, etc. Laser cladding, which can enhance the mechanical properties of the rail by creating a coating, has received great attention in the area of the rails due to the attractive advantages such as low input heat, small heat-affected zone, and small deformation. In this paper, recent developments in the microstructural characteristics and mechanical properties of a cladded layer on the rail are reviewed. The method of process optimization for enhancing the properties of a cladded layer are discussed. Finally, the trend of future development is forecasted.

Online Monitoring Recognition Theory Based on the Time Series of Chatter

2013 ◽  
Vol 819 ◽  
pp. 160-164
Author(s):  
Yong Xiang Jiang ◽  
Bing Du ◽  
Pan Zhang ◽  
San Peng Deng ◽  
Yu Ming Qi
Keyword(s):  
Time Series ◽  
Chaotic Dynamics ◽  
Online Monitoring ◽  
Vibration Signal ◽  
Threshold Value ◽  
Coarse Grained ◽  
Attractor Dimension ◽  
Machining Chatter ◽  
Recognition Theory ◽  
On Line

On-line monitoring recognition for machining chatter is one of the key technologies in manufacturing. Based on the nonlinear chaotic control theory, the vibration signal discrete time series for on-line monitoring indicator is studed. As in chatter the chaotic dynamics process attractor dimension is reduced, the KolmogorovSinai entropy (K-S) index is extracted to reflected the regularity of workpiece chatter, then the k-S entropy is simplified by coarse - grained entropy rate (CER), which can easily evaluated as chatter online monitoring threshold value. The milling test shows that the CER have a sharp decline when chatter occurre, and can quickly and accurately forecast chatter.

Measurement and interpretation of stress in copper films as a function of thermal history

1991 ◽  
Vol 6 (7) ◽  
pp. 1498-1501 ◽  
Author(s):  
Paul A. Flinn
Keyword(s):  
Mechanical Properties ◽  
Thermal Expansion ◽  
Elastic Modulus ◽  
Thermal History ◽  
Copper Films ◽  
Thermally Induced ◽  
Aluminum Films ◽  
Interconnection Material ◽  
Interconnect Systems

Since copper has some advantages relative to aluminum as an interconnection material, it is appropriate to investigate its mechanical properties in order to be prepared in advance for possible problems, such as the cracks and voids that have plagued aluminum interconnect systems. A model previously used to interpret the behavior of aluminum films proves to be, with minor modification, also applicable to copper. Although the thermal expansion of copper is closer to that of silicon and, consequently, the thermally induced strains are smaller, the much larger elastic modulus of copper results in substantially higher stresses. This has implications for the interaction of copper lines with dielectrics.

Improvement of Solution Type Plasma Spraying Process

2005 ◽  
Vol 502 ◽  
pp. 505-510 ◽  
Author(s):  
Masami Futamata ◽  
Xiaohui Gai ◽  
Toyokazu Mizumoto ◽  
Kimio Nakanishi
Keyword(s):  
Mechanical Properties ◽  
Plasma Spraying ◽  
Hollow Cathode ◽  
Thermal History ◽  
Thermal Spraying ◽  
Physical And Mechanical Properties ◽  
Good Reproducibility ◽  
Solution Type ◽  
Plasma Spraying Process ◽  
Spraying Process

To fabricate thermal spraying coatings with good reproducibility, it is necessary to improve the process of the equalization of both thermal history and impacting behavior of the particles. In this study, the characteristics of the solution type plasma spraying using the hollow-cathode type torch are investigated. The physical and mechanical properties that are different from usual thermal spraying coatings are described. By using solutions including metal ingredients in a state of ion, colloid or sol, thinner coating that cannot be made by conventional plasma spraying methods is formed on various substrates. The coatings are uniform in appearance.

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