Elastoplastic response of functionally graded cemented carbides due to thermal loading

Finite dement formulations are used to simulate the evolution of the elastoplastic response of functionally graded cemented carbides （FGCC） due to thermal loading. The geometry of specimens is an axisymmetric solid cylinder with a two-dimensional gradient. The elastoplastic constitutive relationship is developed by constraint factors. Numerical results show that compressive stresses occur in the surface zone and tensile stresses in the cobalt rich zone when the temperature drops from the initial stress-free temperature of 800 to 0℃. The maximum value of the surface compressive stress is 254 MPa and the maximum value of the tensile stress is 252 MPa in the cobalt rich zones. When the cobalt concentration difference in the specimens is equal to or greater than 0.3, there is pronounced plastic flow in cobalt rich zone. When the temperature heats up from 0 to 800 ℃, the total plastic strain reaches 0.001 4. Plastic flow has a significant effect on the reduction of thermal stress concentration.

Thermal residual stress analysis of diamond coating on graded cemented carbides

Finite element model was developed to analyze thermal residual stress distribution of diamond coating on graded and homogeneous substrates. Graded cemented carbides were formed by carburizing pretreatment to reduce the cobalt content in the surface layer and improve adhesion of diamond coating. The numerical calculation results show that the surface compressive stress of diamond coating is 950 MPa for graded substrate and l 250 MPa for homogenous substrate, the thermal residual stress decreases by around 24% due to diamond coating. Carburizing pretreatment is good for diamond nucleation rate, and can increase the interface strength between diamond coating and substrate.

Novel design and composition optimization of self-lubricating functionally graded cemented tungsten carbide cutting tool material for dry machining

The functionally graded cemented tungsten carbide (FGCC) is a suitable material choice for cutting tool applications due to balanced hardness and fracture toughness.The presence of cobalt and CaF2 composition gradient in FGCC may enhance mechanical as well as antifriction properties.Therefore,structural design of selflubricating FGCC was proposed using Power law composition gradient model and thermal residual stresses (TRSs) as a key parameter.Wherein,S.Suresh and A.Mortensen model was adopted for estimation of TRS,and optimum composition gradient was identified at Power law exponent n =2.The designed material displayed compressive and tensile TRS at surface and core respectively;subsequently fabricated by spark plasma sintering and characterized via scanning electron microscope (SEM),indentation method.The agreement between experimental and analytical values of TRS demonstrated the effectiveness of intended design model in the composition optimization of self-lubricating FGCC.This work will be helpful in implementation of dry machining for clean and green manufacturing.