| 1. |
- Joshi, S. V., et al.
(författare)
-
Evidence of accelerated thermal cycling test schedules influencing the ranking of zirconia-base thermal barrier coatings
- 1995
-
Ingår i: Journal of Thermal Spray Technology. - Materials Park, OH, United States : ASM International. ; 4:3, s. 275-279
-
Tidskriftsartikel (refereegranskat)abstract
- Thermal barrier coatings (TBCs) often encounter temperature cycling in the course of normal operation. In the absence of actual or simulated engine test facilities, accelerated furnace thermal cycling experiments are frequently devised to evaluate the response of various TBCs. This study, which deals with yttria-stabilized and magnesia-stabilized zirconia systems, shows that the performance of a TBC is significantly governed by the severity of the time-temperature schedule employed. More importantly, the ranking of the two zirconia-base TBCs also is influenced by the adopted thermal cycling test schedule. These findings have ramifications in the design of suitable accelerated tests for TBC evaluation.
|
|
| 2. |
- Shariff, S. M., et al.
(författare)
-
Parametric influence on cut quality attributes and generation of processing maps for laser cutting
- 1999
-
Ingår i: Journal of Laser Applications. ; 11:2, s. 54-63
-
Tidskriftsartikel (refereegranskat)abstract
- Laser cutting is an attractive alternative to conventional cutting methods due to its many inherent advantages. However, notwithstanding its promise for processing diverse categories of materials, the understanding of the subject is incomplete. Although numerous processes are known to significantly influence cutting quality, comprehensive data of practical utility - such as identification of processing regimes to achieve optimum cut surface attributes - remain yet to be generated. The present article establishes a methodology to develop such "processing maps" and illustrates their utility by using laser cutting of mild steel and commercially pure titanium as case studies. The processing maps can be constructed based on any chosen cut quality criteria and can be used to optimize the process on the basis of operational costs. Results reveal that, for achieving good quality cuts, such processing regimes constitute only a narrow region within the wide operating window for mere cuttability and vary substantially with material-assist gas combination. Typically, the operating window for inert gas-assisted cutting is narrower than that for oxygen-assisted cutting involving an exothermic oxidation reaction, which contributes significantly to the overall energy input to the cutting front. The influence of the two major process parameters, laser power and cutting speed, on cut quality attributes such as surface roughness, kerf width, heat affected zone, and cut surface morphology is also discussed in detail. The experimental results have also been compared with theoretical predictions of a scaling law for laser cutting. © 1999 Laser Institute of America.
|
|
| 3. |
- Sundararajan, G., et al.
(författare)
-
A Comparative Study of Tribological Behavior of Plasma and D-Gun Sprayed Coatings under Different Wear Modes
- 1998
-
Ingår i: Journal of Materials Engineering and Performance. ; 7:3, s. 343-351
-
Tidskriftsartikel (refereegranskat)abstract
- In recent years, thermal sprayed protective coatings have gained widespread acceptance for a variety of industrial applications. A vast majority of these applications involve the use of thermal sprayed coatings to combat wear. While plasma spraying is the most versatile variant of all the thermal spray processes, the detonation gun (D-gun) coatings have been a novelty until recently because of their proprietary nature. The present study is aimed at comparing the tribological behavior of coatings deposited using the two above techniques by focusing on some popular coating materials that are widely adopted for wear resistant applications, namely, WC-12%Co, Al2O3, and Cr3C2-NiCr. To enable a comprehensive comparison of the above indicated thermal spray techniques as well as coating materials, the deposited coatings were extensively characterized employing microstructural evaluation, microhardness measurements, and XRD analysis for phase constitution. The behavior of these coatings under different wear modes was also evaluated by determining their tribological performance when subjected to solid particle erosion tests, rubber wheel sand abrasion tests, and pin-on-disk sliding wear tests. The results from the above tests are discussed here. It is evident that the D-gun sprayed coatings consistently exhibit denser microstructures and higher hardness values than their plasma sprayed counterparts. The D-gun coatings are also found to unfailingly exhibit superior tribological performance superior to the corresponding plasma sprayed coatings in all wear tests. Among all the coating materials studied, D-gun sprayed WC-12%Co, in general, yields the best performance under different modes of wear, whereas plasma sprayed Al2O3 shows least wear resistance to every wear mode.
|
|
