Banca de DEFESA: ERIJANIO NONATO DA SILVA
Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.STUDENT : ERIJANIO NONATO DA SILVA
DATE: 27/01/2020
TIME: 09:00
LOCAL: Sala 414 do CTEC - UFRN
TITLE:
STUDY OF SUBSTITUTION OF COBALT BY THE INVAR ALLOY IN THE HARDMETAL
KEY WORDS:
Cemented carbide; WC-Co; SPark Plasma Sintering; Invar alloy; Hardmetal.
PAGES: 136
BIG AREA: Engenharias
AREA: Engenharia Mecânica
SUBÁREA: Processos de Fabricação
SPECIALTY: Processos de Fabricação, Seleção Econômica
SUMMARY:
Hard metals are widely used in the metalworking industry because of their excellent hardness, good toughness and wear resistance properties. These composites are composed of a hard phase tungsten carbide (WC) mixture and a metal binder, usually cobalt (Co) (or other metals such as iron (Fe), nickel (Ni)). However, cobalt is the most widely used binder due to its good properties, especially wettability. However, this metal presents some dilemmas, such as high cost and toxicity. Given this, this research seeks to employ an alternative binder in cermets that provides properties similar to cobalt, this metal is Invar alloy (Fe 36% Ni) which has a low coefficient of thermal expansion, making it attractive in applications involving temperature changes, as is the case with machining. Samples are fabricated using Spark Plasma Sintering (SPS), which provides rapid sintering and good densification. WC-10% (Fe, Ni) samples were sintered with isothermal thresholds of 1100, 1200 and 1300 ºC. WC-10% Co samples were sintered with 1200 ºC level for comparison. The results show that the microstructure presents a good distribution of WC and binder, decreased porosity and abnormal growth of WC with the increase of isothermal plateau temperature. In addition, the eta phase was found at temperatures of 1200 and 1300 ºC. Dilatometry tests showed that WC-10% (Fe, Ni) has a coefficient of thermal expansion of 5.11 x10-6 ° C-1, whereas WC-10% Co has 6.33 x10-6 ° C -1, showing that the low thermal expansion effect was achieved for WC-Invar. The highest densification achieved in WC-10% (Fe, Ni) is 98.9%. The increase of the isothermal level increased the densification, hardness, compressive strength and modulus of elasticity. WC-10% (Fe, Ni) sintered at 1100 ° C had a hardness of 1777 HV, surpassing WC-Co cermets found in the literature, and fracture toughness of 15.6 MPa m1 / 2. WC-10% (Fe, Ni) sintered at 1300 ° C had the highest compressive strength, 376 MPa, highest modulus of elasticity, 990 GPa, and highest hardness, 1992 HV. Given these results, the Invar alloy (Fe-36% Ni) produced in this research provided WC-alloy cermets compared to WC-Co with excellent microstructural characteristics, very low thermal expansion, high hardness with significant toughness and good compressive strength.
BANKING MEMBERS:
Presidente - 778.819.314-34 - MARCELLO FILGUEIRA - UENF
Interno - 1350249 - RUBENS MARIBONDO DO NASCIMENTO
Interna - 1481705 - SALETE MARTINS ALVES
Externa à Instituição - ALESSANDRA AGNA ARAÚJO DOS SANTOS - UENF