File:Alloys of tungsten by diffusion (1920) (14597324588).jpg

Identifier: alloysoftungsten00hars (find matches)
Title: Alloys of tungsten by diffusion
Year: 1920 (1920s)
Authors: Harsch, John William
Subjects: Tungsten alloys Diffusion Theses
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Contributing Library: University of Illinois Urbana-Champaign
Digitizing Sponsor: University of Illinois Urbana-Champaign

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kilowatts per hour at 1200° G. The heating unit was surroundedby a jacket of magnesia and asbestos. The temperature v/as controlled by the use of a platinum-platinum lCffo rhodium thermocouple, accurately calibrated in con-nection with a Siemens-Halske millivoltmeter. No attempt at con-trol closer than 5° C. was made, since very accurate temperaturecontrol was not necessary in this work. Treatments in this furnace were carried out in a por-celain boat in which the tungsten was surrounded by the alloyingmetal, or, in carbonization treatments, by illuminating gas, whichwas passed through the furnace. b. The second furnace used was a small Hoskins ni-chrome-wound resistance furnace (Fig. II.), using one kilowattper hour at 1200° C. The heating chamber was two inches in dia-meter and two and one-half inches in depth. This furnace wasused in the twenty-four and thirty-six hour tests, where tempera-tures up to 1200° C. were being used. In the preparation of alloys in this furnace, Dixon
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12 graphite crucibles were used, and powdered retort carbon was usedas a cover. The temperature control was the same as that used infurnace Ho, I. c. A gas fired furnace (Fig. III.) of the pot typewas used in all tests requiring temperatures above 1200° C. andup to 1600° C. Fig. III. sufficiently explains the constructionof this furnace. Temperature measurement was made here by the use ofa Leeds and Northrup optical pyrometer. Graphite crucibles v/ere used and the alloy protectedby powdered carbon. (2) Grinding and Polishing Apparatus. The grinding was done on a machine carrying four gradesof emery wheels. After a specimen had been ground down on theemery wheels, it was polished successively on numbers 1, 0, 00,and 000 emery paper. The 0000 grade of emery paper has generallybeen found to scratch the specimen, and therefore it has not beenused. After polishing on 000 paper, specimens were further po-lished on broadcloth saturated with levigated alumina yf2. Thishas proved a v-ry quic

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