Unit Manufacturing Processes Issues and Opportunities in Research (1995) / Chapter Skim
Currently Skimming:
5 Structure-Change Processes
5 Structure-Change Processes
Pages 67-78
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 67... ...
Structure change can be achieved easily in iron-carbon alloys using straightforward thermal treatments that rely on the change in solubility for carbon and alloying elements that accompany iron's allotropic transformations. As expected, mechanical properties vary with the structure.
|
From page 68... ...
However, the thermal treatment practice is handicapped by the low thermal diffusivity inherent to ceramics. Also, slow heating and cooling rates are used to minimize risk of cracking by thermal stresses.
|
From page 69... ...
SURFACE TREATMENT Many coating processes have been developed to deposit microthin films that allow close control of coating thickness and composition not possible with traditional surface treatment processes (e.g., surface hardening, electroplating, and plasma spraying)
|
From page 70... ...
Control of compound stoichiometry requires coupling of the gas admission rate with the coating-flux generation rate. All the thin-film deposition technologies mentioned above, as well as the more recently developed microwave-assisted plasma deposition processes, are in commercial use to support integrated circuit fabrication.
|
From page 71... ...
Laser heat treatment of alloy steels can significantly increase their strength, toughness, sliding wear resistance, and abrasive wear resistance. The microstructure formed near the surface is essentially dislocated packets of martensite surrounded by retained austenitic films.
|
From page 72... ...
Laser cladding is similar to laser surface alloying except that the powder constituents introduced into the melt pool are also melted by the laser beam. The main objective in laser cladding is to overlay a surface or substrate with another material that has a different chemistry by melting a thin interracial layer to produce a metallurgical bond with minimum dilution of the clad layer.
|
From page 73... ...
Both developments permit rapid, in-line structure-change processing, which eliminates the need for batch processing, and hence in-plant storage IS mlnlmlZleC .. Thermal Treatment The technology base related to thermal treatment processes (e.g., annealing, normalizing, spherodizing, solution treatment, aging, hardening, tempering, homogenizing)
|
From page 74... ...
and cracking during thermal processing. Improved thermal treatment processes for structure change of metal alloys require robust sensors to monitor furnace atmosphere and conditions (temperature, partial pressures, flow patterns)
|
From page 75... ...
Understanding process characteristics and the mechanisms involved in the generation of coating flux will enable process models to simulate film deposition so that coating processes can be designed. Process development now depends on trial and error to identify acceptable processing conditions.
|
From page 76... ...
As a result, the laser loses some of its unique advantages.) Progress in laser surface treatment must include the development of alloys optimized for laser treatment.
|
From page 77... ...
1987. Controlled Vacuum Arc Material Deposition Method and Apparatus.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.