EFFECT OF BINDER COMPOSITION AND SINTERING TEMPERATURE ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF WC-7(Ni,Fe) HARD ALLOYS PREPARED BY FREE CAPSULE HIP TECHNIQUE

<p class="AMSmaintext">In this research, WC-7(Ni,Fe) hard alloys were prepared by ball milling, cold compaction and finally consolidated by hot isostatic pressing. The effect of binder composition and sintering temperature were investigated in term of the microstructure, density and mechanical properties of sintered samples. Density of hard alloys was measured by the Archimedes' principle while the microstructure was observed using a scanning electron microscope. The Vickers hardness was investigated at load of 30KG and the fracture toughness was calculated based on the Palmqvist crack method. The results revealed that the density of sintered samples was obtained in the range of 14.65 to 14.8 g/cm³ meanwhile the measured Vicker hardness and fracture toughness were respectively achieved from 1260 to 1520 HV30 and 11,7 to 17,5 MPa.m^1/2 depending on the binder composition and sintered temperature.</p>

Characterization and Fracture Toughness on AISI 8620 with Hard Coatings

The present studies characterize and evaluate the fracture toughness at the surface AISI 8620 with hard coating. The hard coatings FeB and Fe2B were formed using the boriding dehydrated paste at temperatures 1223 and 1273 K with 6 and 8 h exposure time, respectively. The presence of hard coatings formed on the surface AISI 8620 were confirmed by the classical metallographic technique combined with X-ray diffraction analysis. The distribution of alloying elements was determined by Energy Dispersive Spectroscopy (EDS). The fracture toughness of the hard coatings on AISI 8620 was estimated using a Vicker microindentation induced fracture testing of 15 and 35 μm from the surface, applying four load (0.49, 0.98,1.96 and N). The microcrack generated at the corner of the microindentation was considered as an experimental parameter and the tree model Palmqvist crack model was employed to determine the fracture toughness. The adherence of the hard coatings/substrate was evaluate in qualitative form though the VDI 3198 by testing Rockwell C and observed by Scanning Electron Microscopy (SEM). The formation of hard layers was obtained in the range of 100-130 μm, results of XRD present phases FeB, Fe2B, CrB and MnB, the values obtained of Kc are in the range of 2.3 to 4.1 MPam1⁄2 and results of acceptable adhesion HF4 patterns for conditions 6 h of treatment

Evaluation Hard Layers in Steel AISI 8620

In the present study, identify the fracture toughness and strength adhesion of borided layers in Steel AISI 8620 by boriding dehydrated paste. The formation of the borided at a temperature range of 1173, 1223 and 1273 K for 4, 6 and 8 h. X-ray diffraction analysis revealed peak of FeB, Fe2B, MoB and CrB and The distribution of alloying elements was detected by means of energy dispersive Spectroscopy (EDS), the Fracture toughness of the layers is estimated at 15 and 30 um from surface using different loads indentation Vickers, using Palmqvist crack model, the adherence of the layer/substrate was evaluate in qualitative form though the Rockwell C. The fracture toughness of the borides depends strongly on temperature and time boriding. Also, good adhesion is obtained around the Rockwell C indentation prints on the borided layer-substrate-interface.

Formation of Hard Layers in Tool Steels

In the present study, identify the fracture toughness and strength adhesion of borided layers on grade tools steels by Boronizing, two commonly used steel AISI 4140 and AISI 9840 are considered, the steels contain 1.0 - 0.8 wt% Cr and 0.20 - 0.25 wt% Mo, respectively. The formation of the borided layers was carried out by the powder pack boriding process at a temperature range of 1273 K for 4, 6 and 8 h. X-ray diffraction analysis revealed peak of FeB, Fe2B and CrB, the Fracture toughness of the layers is estimated at 15 and 30 um from surface using four different Vickers indentation loads, using Palmqvist crack model, the adherence of the layer/substrate was evaluate in qualitative form though the Rockwell C. The fracture toughness of the borides depends strongly on temperature and time bronzing. Also, good adhesion is obtained around the Rockwell C indentation prints on the borided layer-substrate-interface.

Fracture Indentation on AISI 1018 Borided Steels

Fracture indentation was applied to estimate the fracture toughness of AISI 1018 borided steels. The Fe2B hard layers were formed using the powder-pack boriding process for two temperatures with 4 and 8 h of exposure times. The fracture toughness of the iron boride layer of the AISI 1018 borided steels was estimated using a Vickers microindentation induced-fracture testing at distances of 15 and 30 m from the surface, applying four loads (0.49, 0.98, 1.96 and 2.9 N). The microcracks generated at the corners of the Vickers microindentation were considered as experimental parameters, which are introduced in a Palmqvist crack model to determine their corresponding fracture toughness KC. As a result, the experimental parameters, such as exposure time and boriding temperature are compared with the resulting fracture toughness of the borided phase.