TAILIEUCHUNG - Volume 07 - Powder Metal Technologies and Applications Part 9

Tham khảo tài liệu 'volume 07 - powder metal technologies and applications part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | a b 0 d Fig. 4 Schematic drawing of microstructure of tungsten sintered at different temperatures before being immersed into molten copper a 1100 C 2010 F b 1350 C 2460 F c 1600 C 2910 F d 2800 C 5070 F . 500x. Source Ref 16 Infiltrated bodies that have a continuous skeleton phase above approximately 65 vol can be shaped only by machining while those having a smaller proportion of refractory metal dispersed as loose grains in the ductile metal matrix are plastically deformable at elevated temperatures Ref 8 . Soldering brazing or plating of the infiltrated product is aided by generally smooth surface films or high contents of infiltrant metal. The preceding binary systems illustrate combinations of two metals of widely differing melting temperatures that can be advantageously produced to near-net shape and full density by infiltration. Nickel also can be infiltrated into tungsten but equilibrium at liquid-phase temperature causes severe attack of the refractory metal and requires careful process control to prevent incomplete penetration due to diffusion solidification. Coarse tungsten powder helps to produce compacts with larger capillary channels for better penetration. High heating rates especially after about 90 of the absolute melting temperature of nickel is reached improve infiltration conditions. If nickel is alloyed with copper the solubility of tungsten in the liquid phase decreases as the copper percentage is increased. Infiltration is more practical Ref 8 for heavy alloy systems because tungsten powder and process control requirements are less stringent. If nickel is alloyed with iron however the solid-liquid phase interaction is similar to the binary tungsten-nickel system and infiltration again is more difficult. The same principle applies to the more complex refractory metal systems with nickel-chromium and cobalt-chromium alloys. Nevertheless skeleton bodies of tungsten and molybdenum as well as bodies of binary 85W-15Cr and 75W-25Cr alloys can be .

TỪ KHÓA LIÊN QUAN
Đã phát hiện trình chặn quảng cáo AdBlock
Trang web này phụ thuộc vào doanh thu từ số lần hiển thị quảng cáo để tồn tại. Vui lòng tắt trình chặn quảng cáo của bạn hoặc tạm dừng tính năng chặn quảng cáo cho trang web này.