scholarly journals Correlation Between the Indentation Properties and Microstructure of Dissimilar Capacitor Discharge Welded WC-Co/High-Speed Steel Joints

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2657 ◽  
Author(s):  
Giovanni Maizza ◽  
Renato Pero ◽  
Frediano De Marco ◽  
Takahito Ohmura
Keyword(s):  
High Speed ◽  
Weld Zone ◽  
Base Material ◽  
High Speed Steel ◽  
Cemented Carbide ◽  
Uniaxial Pressure ◽  
High Temperature Strength ◽  
Transitional Layer ◽  
Capacitor Discharge ◽  
High Level

The welding of cemented carbide to tool steel is a challenging task, of scientific and industrial relevance, as it combines the high level of hardness of cemented carbide with the high level of fracture toughness of steel, while reducing the shaping cost and extending the application versatility, as its tribological, toughness, thermal and chemical properties can be optimally harmonised. The already existing joining technologies often impart either insufficient toughness or poor high-temperature strength to a joint to withstand the ever-increasing severe service condition demands. In this paper, a novel capacitor discharge welding (CDW) process is investigated for the case of a butt-joint between a tungsten carbide-cobalt (WC-Co) composite rod and an AISI M35 high-speed steel (HSS) rod. The latter was shaped with a conical-ended projection to promote a high current concentration and heat at the welding zone. CDW functions by combining a direct current (DC) electric current pulse and external uniaxial pressure after a preloading step, in which only uniaxial pressure is applied. The relatively high heating and cooling rates promote a thin layer of a characteristic ultrafine microstructure that combines high strength and toughness. Morphological analysis showed that the CDW process: (a) forms a sound and net shaped joint, (b) preserves the sub-micrometric grain structure of the original WC-Co composite base materials, via a transitional layer, (c) refines the microstructure of the original martensite of the HSS base material, and (d) results in an improved corrosion resistance across a 1-mm thick layer near the weld interface on the steel side. A nano-indentation test survey determined: (e) no hardness deterioration on the HSS side of the weld zone, although (f) a slight decrease in hardness was observed across the transitional layer on the composite side. Furthermore, (g) an indication of toughness of the joint was perceived as the size of the crack induced by processing the residual stress after sample preparation was unaltered.

scholarly journals Defect formation and microstructural changes in friction stir welds between pure copper and a brass alloy

2009 ◽  
Vol 15 (S3) ◽  
pp. 79-80 ◽  
Author(s):  
Rui M. Leal ◽  
Carlos Leitão ◽  
Altino Loureiro ◽  
Dulce M. Rodrigues
Keyword(s):  
High Speed ◽  
Defect Formation ◽  
Position Control ◽  
Pure Copper ◽  
Base Material ◽  
High Speed Steel ◽  
Tool Geometry ◽  
Slight Reduction ◽  
Friction Stir ◽  
Brass Alloys

AbstractSeveral attempts have been made in the last few years for joining similar pure copper and brass alloys using the solid state friction stir welding (FSW) process. For both material types, all the works performed reported that the production of defect free welds is largely dependent on the correct choice of process parameters. It was also observed that, despite grain refinement occurred in the centre of all the welds, the welds in copper showed a slight reduction in strength, when compared to that of the base material, as opposed to welds in brass alloys, for which an increase in strength was observed. Regardless of the encouraging results obtained in similar FWS of these materials, in the knowledge of the authors, few reports exist concerning dissimilar joints between them. In his work, dissimilar welds between Cu DHP cooper plates and Cu-Zn 37 brass plates, both of 1 mm thickness, with the brass plate positioned in the advancing side of the tool, were analysed. Welds were carried out with a solid tool made of high speed steel. Tool geometry was characterized by a tool shoulder of 10 mm in diameter, containing a conical cavity of 6 degrees, and a threaded probe of 3 mm in diameter. Welds were done in a milling machine, in position control, using the working parameters indicated in table 1.

scholarly journals Effect of Pulsed Laser Ablation on the Increase of Adhesion of CRN Coating-Substrate

2018 ◽  
Vol 26 (43) ◽  
pp. 61-70
Author(s):  
Paulína Zacková ◽  
Lucia Števlíková ◽  
Ľubomír Čaplovič ◽  
Martin Sahul ◽  
Vitali Podgurski
Keyword(s):  
Laser Ablation ◽  
Residual Stresses ◽  
High Speed ◽  
Substrate Surface ◽  
Base Material ◽  
High Speed Steel ◽  
Cobalt Content ◽  
Deposition Process ◽  
Adhesion Behavior ◽  
Surface Laser

Abstract The contribution deals with analysis of the influence of the substrate surface laser ablation before deposition process to improve the adhesion of coating-substrate system. The coatings were applied to the high-speed steel 6-5-2-5 (STN 19 852) and WC-Co cemented carbide with cobalt content of 10 wt%. LAteral Rotating Cathodes (LARC®) process was chosen for evaporation of individual CrN layers. Influence of laser ablation on the substrate morphology, structure, roughness, presence of residual stresses inside the substrates and layers and their adhesion behavior between the layers and the base material was studied. Scanning electron microscopy fitted with energy dispersive spectroscopy was utilized to investigate morphology and fracture areas of substrates with CrN layers. X-ray diffraction analysis was employed to detect the residual stresses measurements. Adhesion between the coatings and substrate was analyzed using “Mercedes” testing.

Fatigue behavior of two notched cutting tool materials – High speed steel and cemented carbide

2020 ◽  
Vol 62 (3) ◽  
pp. 265-270
Author(s):  
Zainul Huda ◽  
Muhammad Hani Ajani ◽  
Muhammad Saad Ahmed
Keyword(s):  
High Speed ◽  
Cutting Tool ◽  
Fatigue Behavior ◽  
High Speed Steel ◽  
Cemented Carbide ◽  
Tool Materials ◽  
Cutting Tool Materials

Study on Preparation and Machining Performance of SiC/Cu Composites

2012 ◽  
Vol 174-177 ◽  
pp. 425-428
Author(s):  
Nian Suo Xie ◽  
Jin Wang
Keyword(s):  
Surface Roughness ◽  
High Speed ◽  
High Speed Steel ◽  
Cemented Carbide ◽  
Pulse Interval ◽  
Machining Performance ◽  
Electro Discharge Machine ◽  
Electro Discharge Machining ◽  
Cutting Surface ◽  
Discharge Machine

SiC/Cu composite materials were fabricated by powder metallurgy, and microstructure of composite was analyzed by means of metallographic microscope. The high speed steel tool and cemented carbide tool are used as cutters, and machining performance of SiC/Cu Composites were studied by cutting lathe and wire-electro discharge machine. The relationship between wire-electro discharge machining cutting speed and pulse interval were studied by wire-electro discharge machine. The results show that the composite cutting surface roughness increases with increasing of the content of SiC particles when the size of SiC is 40μm, while composite cutting surface roughness decreases with increasing of the content of SiC particles when the size of SiC is 20μm, the cemented carbide tolls have longer life than high-speed steel tools. The surface roughness of composite increases with the increasing of source voltage, but it decreases with increasing of pulse interval in the wire-electro discharge machining cutting conditions.

scholarly journals High Performance Valve Seat Materials for CNG Powered Combustion Engines

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 4860
Author(s):  
Andrzej Romański ◽  
Elżbieta Cygan-Bączek
Keyword(s):  
High Speed ◽  
High Performance ◽  
Base Material ◽  
High Speed Steel ◽  
Wear Test ◽  
Gas Temperature ◽  
Valve Seat ◽  
Test Procedures ◽  
Gasoline Engines ◽  
Engine Valves

The conventional copper infiltrated high speed steel (HSS) valve seats used in gasoline engines are not suitable for CNG combustion because the exhaust gas temperature is at least 80 °C higher, which drastically shortens the service life of the engine valves. Therefore, a proprietary high-alloy HSS-base material was designed to combat hot corrosion and mechanical wear of valve seat faces in CNG fuelled engines. A batch of −100 mesh water atomized HSS powder was commissioned. The powder was vacuum annealed in order to reduce oxygen content and increase its compressibility. To improve the final part machinability, 1.2% MnS was admixed to the HSS powder prior to compaction. The green compacts were sintered at 1135 °C in nitrogen to around 83% TD and subsequently infiltrated with a copper alloy. After installing the valve seat components on a cylinder head, the engine was tested for 100 h according to the automotive industry valve seat wear test procedures. Both the periodic 8-h checks as well as the final examination of the valve seats showed very slow wear, indicating their suitability for CNG powered engines.

Contact interaction peculiarities at the boundary of layers of «structural steel–high-speed steel» hot-forged powder bimetal

2018 ◽  
pp. 11-22
Author(s):  
Yu. G. Dorofeyev ◽  
V. Yu. Dorofeyev ◽  
A. V. Babets ◽  
Eu. N. Bessarabov ◽  
O. N. Romanova ◽  
...  
Keyword(s):  
Structural Steel ◽  
High Speed ◽  
Hot Forging ◽  
Base Material ◽  
High Speed Steel ◽  
Contact Boundary ◽  
Adhesive Interaction ◽  
Layer Material ◽  
Working Layer ◽  
Cold Pressed

The main problem in the production of bimetals (BMs) is the need to ensure adhesive interaction at the contact boundary of layers to prevent their peeling during operation. Hot forging of porous preforms (HFPP) provides the possibility of obtaining high-density powder BMs with a minimum amount of pores both in the volume of the layer material and at the layer interface to increase adhesion strength. Production of hot-forged powder BMs may involve mixing of working layer and substrate charge materials, which can lead to uncontrolled interface «blurring». This study uses the previously proposed method for pre-pressing of hard-to-deform material powder to produce «structural steel – high-speed steel» porous BM preforms. Two-layer cylindrical ∅20×30 mm samples were obtained in order to determine mechanical properties and conduct structural analysis. The BM base material was PK40 steel, and the working layer was atomized powder of M2 high-speed steel featuring satisfactory compressibility properties. The porous preforms of BM samples were pressed in a specially designed mold at a hydraulic press enabling two-sided pressing of two-layer powder moldings with predetermined distribution of layer densities and strengths. Cold-pressed BM preforms were sintered in protective environment, and then subjected to hot repressing using a laboratory drop hammer. Some preforms were examined as sintered. In addition, hot repressing of cold-pressed green preforms was performed. Satisfactory process strength of the working layer material is observed at its porosity (Pwl) in the range from 34 to 45 %. When Pwl> 45 %, powder is not molded, and at Pwl< 34 % the working layer delaminates. The maximum layer bonding strength and thermal shock resistance of BM provides the use of a flow route that involves preliminary sintering of cold-pressed preforms and subsequent hot forging. The optimum pressure of working layer pre-pressing is 145 MPa.

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