摘要:

Shock compression processing is emerging as a novel technique for fabrication of esoteric materials. Not only can metal and ceramic powders be dynamically consolidated, but both equilibrium and non-equilibrium structures can be synthesized under the high pressure regime during the passage of shock waves of sufficient magnitude and duration. The shock waves can be generated by impact from a plate (accelerated by compressed gas or detonation of explosive) or direct contact with explosives. Very hard metallic and ceramic powders, as well as those powders that cannot be processed by conventional powder processing techniques can be easily compacted to solid densities. The bonding mechanisms in shock compaction involve the rapid and intense deposition of shock energy, preferentially at interparticle regions, resulting in extensive plastic deformation. This may lead to interparticle welding due to partial melting or simply solid-state diffusional bonding.

ISSN:0898-2090    

DOI:10.1080/10426918808953217

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The manuscript describes plasma carburizing process with an emphasis on process parameters rather than structure-property relationships. Following a brief description of the glow-discharge plasma the results on several steels are presented to show the effect of process parameters on the kinetics of carburizing.

ISSN:0898-2090    

DOI:10.1080/10426918808953218

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The demand for high performance in the combustion equipment used in the automobile and aerospace industries is creating renewed interest in the use of ceramic protective coatings on metal surfaces. Sometimes, thick coating layers are required as thermal barriers or for wear resistance and hardness. Although plasma spraying is one of the promising processes available for depositing thick ceramic coatings onto metal surfaces, the presence of porosity in the coating coupled with lack of corrosion resistance of the coated materials, and the generally low strengths of both the coating layer and the coating-matrix interface may limit the use of the process. HIP treatment of ceramic coatings allows one to obtain dense coatings and also to increase the interfacial bond strength. The present paper reviews the recent advances in the post-HIPing of ceramic coatings as well as the use of HIP for sinter-coating by which a ceramic powder compact is sintered and bonded simultaneously to a metal surface.

ISSN:0898-2090    

DOI:10.1080/10426918808953219

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A new concept for materials processing in space with the expectation of future manufacturing in that environment exploits the ultra-vacuum component of space for thin-film epitaxial growth. The unique low earth orbit space environment is expected to yield vacuum levels of 10-14torr or better, semi-infinite pumping speed and large ultra-vacuum volume (10's to 100's of cubic meters) without walls. These space ultra-vacuum characteristics promise major improvement in the quality, throughput, and new materials and devices possibilities of epitaxially grown thin films, especially in the area of semiconductors for microelectronics use. For such improved crystalline thin-film materials there is expected a very large value added from space ultra-vacuum processing, and as a result the application of the epitaxial thin-film growth technology to space could lead to major commercial efforts in space.

ISSN:0898-2090    

DOI:10.1080/10426918808953220

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Silicon carbide was chemically vapor deposited on the small particles in the fluidized bed reactor. Methyltrichlorosilane and hydrogen were used as reactants and in some cases argon was added as a fluidizing gas. Thirty-one coating runs were carried out where coating temperature, methyltrichlorosilane concentration and fluidizing gas composition were varied systematically. The deposit composition was found to be beta-SiC or mixture of beta-SiC and silicon by X-ray diffractometry. The coating temperature affected the deposit composition. From the results of the coating experiment, the model of the CVD processes was presented, which was based on the mass transfer mechanism. This model explained the experimental results fairly well.

ISSN:0898-2090    

DOI:10.1080/10426918808953221

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

SiC matrix composite components have been fabricated by infiltrating and overcoating fiber preforms of graphite, alumina, and SiC via chemical vapor deposition (CVD). The degree of CVD densification could be controlled to yield vacuum tight components as well as porous open mesh structures where only the fiber was coated. These components have been fabricated in a wide variety of shapes including baskets, tubes and corrugated panels. The CVD process has been successfully scaled up to produce panels 80 cm by 80 cm. The morphology, chemistry, and geometry of the fiber was found to have a significant effect on the deposition process. Thus, process conditions had to be modified based on the fiber being infiltrated. These components were subjected to 1400 C temperature treatments including operation in gas-fired furnaces. After 2000 hours of testing in a gas-fired furnace at 1300 C, the SiC composite tubes have remained intact and un cracked. This suggests that the monolithic SiC coating is the controlling material and not the fibers. Hence, in light-load applications these structures still have useful lifetimes.

ISSN:0898-2090    

DOI:10.1080/10426918808953222

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

This paper deals with the fabrication processes of short fiber reinforced metal matrix composites and controlling parameters for squeeze casting. It refers to the preparation of fiber preforms, heat-exchange between fiber and molten metal, infiltration pressure, optimum fabrication conditions and die design.

ISSN:0898-2090    

DOI:10.1080/10426918808953223

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The objective of this study was to ascertain the effect of tool wear on surface roughness and develop a more thorough understanding of the process variables affecting surface roughness. Experimental data from a finish turning operation on gray cast iron with uncoated tungsten carbide tools was used to develop a model for surface roughness as a function of cutting speed, feed rate, nose radius of the tool and the amount of wear on the tool. The experiment was statistically designed to minimize the number of runs. Tool wear was treated as a variable notwithstanding the fact that it is one of the responses of the process. The results showed that surface roughness is significantly affected by tool wear and the interactions between tool wear and other variables like cutting speed, feed rate and nose radius. The results also provide better insight into the problem of “adaptive” process control for finish turning operations.

ISSN:0898-2090    

DOI:10.1080/10426918808953224

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor