Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
EVALUATION OF CEMENTED CARBIDE/HIGH SPEED STEEL COMPOSITE SINTERED BY PECS
Submission Author:
Daniella Gualberto Caldeira de Paula , ES , Brazil
Co-Authors:
Daniella Gualberto Caldeira de Paula, João Paulo Alves, Ailana Kröhling Uliana, Mariane Gonçalves de Miranda, Marcelo Bertolete, Izabel Machado, Francisco Briones
Presenter: Daniella Gualberto Caldeira de Paula
doi://10.26678/ABCM.COBEM2021.COB2021-0775
Abstract
Although cemented carbide is a cutting tool widely used in machining, mechanical and thermal cracks may happen owing to lack of fracture toughness. Functionally Graded Materials (FGM) are composites made of two or more different materials tailored in a gradient form. Cemented carbide and high-speed steel are two important and distinct groups of cutting tool materials. For producing a cemented carbide – high-speed steel FGM, these materials were studied firstly as a single homogeneous composite to understand their microstructure behaviour and sintering parameters influence. Therefore, this work aims to evaluate physical and mechanical properties of a cemented carbide – high-speed steel composite with TiC addition and compare them with those of a commercial homogenous cemented carbide tool. For this, cemented carbide (particle size 1.5 µm), high-speed steel (50 µm) and TiC (0.8 µm) powders were sintered varying the TiC volume fraction from 5 to 35% at 1200ºC, under uniaxial pressure of 20 MPa and 2.2 MPa, using the technique of pulsed electric current sintering (PECS). The physical property, relative density, was determined based on the Archimedes principle. The mechanical properties, hardness and fracture toughness were conducted using a Vickers indenter. The results showed a great influence of the sintering pressure on the relative density and, consequently, on the mechanical properties. For the 5% TiC sample sintered at 20 MPa, the relative density was 97.8%, close to the commercial cemented carbide, 98.1%. Considering mechanical properties, the 5% TiC sample obtained the Vickers hardness number of 1242±62 HV and fracture toughness of 12.4±1.3 MPa.m1/2, whereas the commercial sample obtained 1284±176 HV and 13.0±1.3 MPa.m1/2. For samples sintered at 2.2 MPa with TiC addition of 15 to 35%, loss of relative density and mechanical properties were observed as the volume fraction of TiC increased. Except for 15% TiC, which attained higher fracture toughness 13.3±1.0 MPa.m1/2. In this case, the porosity may have changed the fracture mode. In addition, from 25% TiC sample, the amount of iron segregation in the microstructure decreased. The results showed the importance of applying pressure during sintering to achieve the necessary relative density and mechanical properties. Furthermore, it is desirable to control the TiC content in the microstructure to avoid iron segregation and, consequently, residual stress.
Keywords
Cemented Carbide, sintering, density, hardness, fracture toughness
