The effects of microstructure and mechanical properties on the wear resistance of B4C-TiB2 ceramic composite were studied. The composite was hot pressed from a B4C-TiO2 precursor at a temperature range of 1800 and 1850 °C. Both the relative density and amount of TiB2 secondary phase of the B4C-TiB2 composite increased with the amount of TiO2 sintering additive in B4C-TiO2 precursor. The hardness of the composite increased with a secondary phase portion up to 29.8 vol.% TiB2. However, the positive effect of TiB2 secondary phase on the fracture toughness of B4C-TiB2 composite was measured in the complete experimental range, with the highest average attained value of 7.51 MPa·m1/2. The wear resistance of B4C-TiB2 composite increased with both the hardness and fracture toughness. The best wear resistance was achieved with the composite with a higher hardness value of 29.74 GPa. This sample consisted of 29.8 vol.% TiB2 secondary phase and reached a fracture toughness value of 6.91 MPa·m1/2. The fracture-induced mechanical wear of B4C-TiB2 composite was the main wear mechanism during the pin-on-disc wear test. Transgranular fracture with pullout of the surface and micro-crack formation in the direction perpendicular to the wear direction was observed on the worn surfaces.

This study investigated the microstructure and properties of soldered joints of AISI 304 stainless steel and PMMA thermoplastic or AW-1050A aluminum alloys made using Resistance Element Soldering (RES) technology. The bimetallic element used in RES provided a mechanical joint with a thermoplastic or aluminum alloy and a soldered joint with AISI 304 steel using Sn60Pb40 solder in the core of the element. The solder in combination with the Chemet CHM-A-014 flux wetted the AISI 304 steel surface very well at a temperature of 225 °C with a contact angle of 14°. During the production of the joints, the solder melted in the bimetallic element on the AISI 304 steel side, while solid solder was retained at the point of contact with the welding electrode. The strength of the joints ranged from 25.5 to 36.4 MPa, which was less than the strength of the solder, and the joints failed at the AISI 304 steel–Sn60Pb40 solder interface. The fracture surface was predominantly formed by the solder. An intermetallic phase of FeSn2 was identified at the interface.

Fibre laser welding of CP780 and TRIP690 steel sheets with a thickness of 1.5 mm was evaluated.Sound welds were obtained at the heat input from 43.3 to 95.0 J mm -1 .The highest 488 and 476 HV0.1 microhardness values were measured in the coarse-grained HAZ of CP780 and TRIP690 steel, respectively.The microstructure in the fusion zone consisted mainly of martensite and lower bainite.The microstructure in the coarse-grained HAZs contained martensite, lower bainite, upper bainite, and retained austenite.The microstructure of the inter-critical HAZs consisted of martensite and ferrite with an increased portion of ferrite with the distance from the fusion zone.The softening regions were indicated in the sub-critical HAZs of both steels.Joint tensile strength exceeded the tensile strength of TRIP690 steel.The apparent elongation was concentrated mainly in TRIP690 steel because of the transformation strengthening of the weld region during the welding process.

Ceramic composites consisting of a boron carbide (B4C) matrix and titanium diboride (TiB2) secondary phase were obtained by reactive sintering from boron carbide powder with 40 and 50wt.% of titanium dioxide (TiO2) additive. The same sintering temperature of 1850?C and pressure of 35MPa, but different sintering times from 15 to 60min, were applied during reactive hot pressing of the composites in vacuum. The effects of TiO2 content and sintering time on phase compositions, microstructures and mechanical properties of the composites were studied. The TiO2 additive enhanced densification of the B4C-TiB2 ceramic composites. Both Vickers hardness and the fracture toughness of the composites increased with prolongation of sintering time. The highest hardness of 29.8GPa was achieved for the composite with 29.6 vol.% of TiB2 obtained by sintering of the precursor with 40wt.% of TiO2 additive for 60min. The fracture toughness reached a maximum value of 7.5MPa?m1/2 for the composite containing 40.2 vol.% of TiB2, which was fabricated by reactive sintering of the precursor with 50wt.% of TiO2 additive for 60min.

Wear of TiAlCN coatings deposited on HCR (High Contact Ratio) gears was studied by the Niemann test during which the tested gears were loaded up to the 12th load stage. The resistance against scuffing was evaluated based on the criteria of allowable roughness (max. Rz 7 µm) and weight loss (max. 10 mg). The extent and character of wear were influenced by coating thickness, contact pressure and meshing frequency. The wear of thicker TiAlCN coatings on the tooth face started with the smoothing of surface protrusions. The next stage of wear was characterized by depletion of TiAlCN coating. After depletion to a thickness of about 2 µm, the layer was pressed into the soft substrate, and it subsequently cracked. At higher load stages, the layer was partially detached, but the critical roughness indicating scuffing was not exceeded. Thinner TiAlCN coating on the tooth flank cracked and fully detached at lower load stages compared to thicker layers and wear of uncoated soft substrate caused the increase in roughness above the critical value representing scuffing.

Wear of nonstandard involute gears with two types of coatings, AlCrN and CrAlSiN, was studied. The coatings were applied by cathodic arc deposition. The gears were tested using a Niemann tester at a graduated load up to the 12th load stage and were compared to noncoated gears. Both Biogear S150 gear oil and PP90 universal hydraulic oil were applied during these tests. The thickness of deposited coatings and wear of gear teeth were studied by SEM and their chemical compositions were determined by EDS analysis. Maximal contact pressure of 1350 MPa was calculated in the region of the tooth flank at the 12th load stage. Maximal frictional stress was also calculated on the tooth flank. The resistance against wear of gears was evaluated based on the critical weight loss and mainly based on the critical surface roughness of gears. The critical roughness was exceeded at the 10th load stage for noncoated gears. For the gears with AlCrN and CrAlSiN coatings, the critical roughness was exceeded at the 11th load stage. Wear of AlCrN and CrAlSiN coatings was nonuniform along the height of tooth. Wear on the tooth flank was characterized by fragmentation of thin coatings and subsequent detaching of fragments from the steel substrate. The steel substrate was worn by microcutting, which caused the highest roughness on the tooth surface. On the tooth pitch, surface protrusions of coatings were smoothed, and coatings cracked and locally detached subsequently. On the tooth face, surface protrusions were also smoothed but coatings remained compact without crack initiations. Both experimental oils, Biogear S150 and PP90, proved to be suitable during Niemann tests as their temperatures did not exceed the limit value of 80 °C.

The submitted contribution deals with the wear of thin coatings applied to convex–concave gearings for gear made from C45E steel. The influence of the tribological characteristics (friction coefficient, wear, adhesion and hardness) of the TiN, TiCN coatings and the combined coating of TiCN + MoS2 on convex–concave gearing is described, from the aspects of scuffing formation. Scuffing tests were done on C–C gears. Coatings were applied by arc–ion-plating (AIP) and magnetron sputter-ion-plating (MSIP) methods. The thickness of the deposited coating and its chemical composition were determined by SEM and EDX analysis. Load-bearing capacity was evaluated by a Niemann tester. The TiCN + MoS2 combined coating with the MoS2 layer on the top reached the lowest coefficient of friction. However, after a rapid wearing of the MoS2 layer, this value dropped to a comparable value of TiCN. The nano-hardness of the TiCN layer was higher in comparison with TiN. Thin and soft MoS2 layers cracked already at lower load levels and separated from the substrate at the 5th load stage. The formation of scuffings for selected coatings documented in this article was solved for convex–concave gearing working also in interaction with Biogear S 150 and Biohyd MS 46 oils.

This article is focused on an analysis of factors negatively affecting the tube production process of tubes made from austenitic stainless steel with a very small diameter of ϕ 0.34 mm. The analysis was concentrated on factors that affect the drawing process stability of the seam tubes where the desired final dimensions—a diameter of ϕ 0.34 mm and a wall thickness of 0.057 mm—are limiting factors. Seam tubes made from steel 1.4306 and 1.4301, from producers KT and EW with a longitudinal weld line made by tungsten inert gas (TIG) welding, were used as blanks for constituent drawing operations. It is desirable to provide sufficient inert gas flow and cooling during the formation of a weld joint in a protective atmosphere chamber. A significant temperature gradient prevents the formation of undesirable Cr23C6 carbides in the heat-affected zone (HAZ) which negatively affects the plasticity and formability of the steel and is the cause of technological fractures.

The effects of strengthening phase in particulate ceramic composites on their properties were studied in presented paper. The experimental materials were a monolithic Si3N4 and particulate ceramic composites consisting of Si3N4 matrix with different additions of the SiC strengthening phase (10 and 20 vol.%). The microstructure, density, hardness and fracture toughness of Si3N4 + SiC ceramic composite materials were compared with monolithic Si3N4 based ceramic material. The addition of SiC particles into the Si3N4 based matrix does not positively influence the phase transformation from alpha-Si3N4 to beta-Si3N4 in Si3N4 + SiC ceramic composite materials, but it affects the growth of prismatic beta-Si3N4 grains and contributes to the creation of fine-grained microstructure. The increase of SiC strengthening phase portion slightly increases relative density of Si3N4 + SiC ceramic composite materials. The hardness of ceramic materials increased from 14.48 GPa at monolithic Si3N4 ceramics to 16.99 GPa at ceramic composite with 20 vol.% SiC. The highest fracture toughness value of 8.30 MPa.m(1/2) was achieved for monolithic Si3N4 ceramics, the lowest value of 7.09 MPa.m(1/2) was achieved for ceramic composite with 20 vol.% SiC.

The effect of sintering temperature in the interval from 1775 to 1850?C on the density, microstructure, hardness and fracture toughness of ceramic composites consisting of a boron carbide matrix and titanium diboride secondary phase was studied. The composites were hot pressed using in situ reaction between boron carbide and 40 wt.% of titanium dioxide additive. The samples were hot pressed at different temperatures but for the constant time of 60min, under the pressure of 35MPa in vacuum of 10 Pa. Both Vickers hardness and fracture toughness of the composites increased with the sintering temperature.Maximal hardness of 29.8GPa and fracture toughness of 6.9MPa?m1/2 were achieved for the composite with 29.6 vol.% of titanium diboride secondary phase sintered at the highest sintering temperature of 1850?C.

The effect of mechanical properties on wear resistance of Si3N4 - SiC composite materials with different portions of SiC strengthening phase was investigated. Properties of monolithic silicon nitride were compared to ceramic composites consisting of Si3N4 matrix with 10 and 20 vol.% SiC. The SiC strengthening phase had a positive effect on the hardness of Si3N4 - SiC ceramic composite materials. Wear resistance of tested ceramic materials was mainly influenced by their fracture toughness. The highest wear resistance value was achieved for material with the highest fracture toughness. Worn surfaces of all experimental ceramic materials were damaged by both microcutting and microcracking mechanism. Microcracking was the predominant wear mechanism mainly at ceramic composites. The wear resistance of SiC-Si3N4 ceramic composites can be described by the model W ~ HV/KIC.

Ceramic composite materials consisting of B4C matrix and Al8B4C7 secondary phase were prepared by in situ reactive sintering of the initial powder mixture B4C-Al with concentration from 5 to 25 wt.% Al sintering additives. The composite samples were hot pressed at the temperature of 1850 °C, pressure of 35 MPa, for 15 min in a vacuum atmosphere. The portion of Al8B4C7 secondary phase increased from 3.3 to 22.1 wt.% when increasing the concentration of Al sintering additive from 5 to 25 wt.% Al. Significant improving of densification and mechanical properties was measured at increasing of Al sintering additive concentration from 5 to 10 wt.% Al. The highest average hardness of 28.74 GPa was achieved when adding 15 wt.% Al sintering additive. The fracture toughness increased with concentration of Al sintering additive in whole concentration range with the highest average value of 5.92 MPa.m1/2 at 25 wt.% Al sintering additives.

The effect of sintering time on the chosen mechanical and tribological properties of silicon nitride (Si3N4) with 5 wt.% of yttrium aluminium garnet (Y3Al5O12) ceramics was investigated. The Si3N4 ceramics sintered for shorter time contained a larger portion of untransformed alpha-Si3N4 phase which has higher hardness compared to the tougher beta-Si3N4 phase. The fracture toughness of Si3N4 ceramics increased with the prolongation of its sintering time. The microcutting wear mechanisms predominated during the grinding of the Si3N4 ceramics with the Al2O3 abrasives. The hardness of ceramic material had a great effect on its wear resistance. The wear of ceramics at friction with 18Cr-8Ni type of austenitic stainless steels was several times higher compared to friction with 14Cr type of ferritic stainless steel. Under these conditions, the microcracking wear mechanisms predominated.

Ceramic composite materials based on boron carbide were hot pressed utilising in situ reaction of boron carbide powder with 40 wt.% of titanium dioxide sintering additive. The samples were prepared at sintering temperature of 1850 degrees C, pressure of 35 MPa, and time of 60 min in vacuum atmosphere of about 20 Pa. Optimisation of sintering regime concentrating on both heating stage of sintering and application of pressure enabled to prepare fully dense ceramic composite materials composed of boron carbide matrix with 29.5 vol.% of titanium diboride secondary phase. The ceramic composite reached average density of 99.31 %, hardness of 29.8 GPa, and fracture toughness of 6.9 MPa.m(1/2).

The subject of this article is the study of influence of sintering time and sintering additives on mechanical properties and wear resistance. Si3N4 with Al2O3+Y2O3 additives (YAG) and Si3N4 with MgO additives was used as an experimental materials. Compositions sintered for 30 min achieved optimal combination the hardness and fracture toughness - 15.05 GPa and 6.87 MPa.m1/2 for Si3N4-MgO and 14.65 GPa and 5.71 MPa.m1/2 for Si3N4 -YAG. Wear was mostly influenced by the hardness of ceramic materials. The specimen with the highest hardness achieved the highest wear resistance. Wear resistance of ceramics decreased with the grain growth and with the transformation progress of narrow α- Si3N4 phase to prismatic β- Si3N4 phase. The wear resistance of the studied ceramics can be described by model V ~ HV-1. Si3N4 -YAG in comparison to Si3N4-MgO has several times greater wear resistance.

Due to the improvement of efficiency of power equipment (heat exchanger), it has been required to change the arrangement of exchanger tube bodies through the minimization of exchanger tubes bending radius. It was necessary to optimize process parameters and functional parts of forming tool to achieve the required parameters of tube bending. On the bending rail, which is one of the main parts of forming tool was used a newly developed type of cast iron with especially suitable characteristics minimizing a coefficient of friction during forming processes. In this paper we present the obtained results and material features in strain area of exc hanger tubes.

This article is focused on analysis of state formation which influences the tubes production process from austenitic stainless steels with diameter circle divide 0.34 mm in a negative way. The problems have been concentrated on factors monitoring which affect the drawing process stability of seem tubes where the desired final dimensions - a diameter circle divide 0.34 mm and a wall thickness 0.057 mm have been limited factors. The seem tube from steel 1.4306 and 1.4301 from producers KRUPP THYSSEN and ERGSTE WESTIG with longitudinal weld line created by TIG welding has been used as a blank for constituent drawing operations. By means of a weld analysis it has been determined that a thermal field creating during a weld formation can cause such material changes which influence to plasticity in a negative way during constituent drawing operations. There is a danger of chromium carbide precipitation along grain boundary in heat affected zone if a weld thermal field isn't sufficiently cooled. These carbides cause plasticity degradation during technological operations with the most intense strain. It is desirable to provide intense inert gas circulation during a weld creation in air protective chamber.

The high-strength steels and tailor welded blanks (TWB) are applied in construction of cars parts to reduction of cars weight [1, 2]. The application of these materials brings possible complicatons during the forming when it proves the considerable influence of stress-strain characteristics differences of the individual parts of TWB what result in non-constant material flow and consequently a negative movement of the weld interface [3, 4]. One of the ways of elimination of this negative effect is to choose a suitable blankholder system with optimal distribution of blankholder forces by using elastic blankholder with adjustable distribution of blankholder forces. Within the bounds of study the experimental blankholder system with elastic blankholder with adjustable distribution of blankholder forces was used [5, 6]. Finite element methods (FEM) simulation has unsubstitutable role n the study of formability of TWB whereby it is possible to determine the values and points of application of the blankholder forces [7, 8]. The FEM simulations results carried out in simulative LS-Dyna software are presented in this article which is focused on achieving weld interface movement minimalization of tailor welded blanks from DP600 and BH220 materials by optimization of blankholder forces [9, 10].

The high-strength steels and tailor welded blanks (TWB) are applied in construction of cars parts to reduction of cars weight [1, 2]. The application of these materials brings possible complicatons during the forming when it proves the considerable influence of stress-strain characteristics differences of of the individual parts of TWB what result in non-constant material flow and consequently a negative movement of the weld interface [3, 4]. One of the ways of elimination of this negative effect is to choose a suitable blankholder system with optimal distribution of blankholder forces by using elastic blankholder with adjustable distribution of blankholder forces. Within the bounds of study the experimental blankholder system with elastic blankholder with adjustable distribution of blankholder forces was used [5, 6]. Finite element methods (FEM) simulation has unsubstitutable role n the study of formability of TWB whereby it is possible to determine the values and points of application of the blankholder forces [7, 8]. The FEM simulations results carried out in simulative LS-Dyna software are presented in this article which is focused on achieving weld interface movement minimalization of tailor welded blanks from DP600 and BH220 materials by optimization of blankholder forces [9, 10].

The forming properties and simulated side impact crash tests of two types of B-pillar reinforcements were analysed. The first B-pillar was drawn from simple blank made of dual phase steel DP600 with thickness of 1.2 mm. The second one was drawn from tailor-welded blank consisting of two dual phase steels DP600 and DP980 with thickness of 1.0 mm. The wall thicknesses in exposed areas of drawn parts were calculated. Both types of B-pillar reinforcements could by drawn without the cracks creation during the drawing process after optimization of blank holder forces. The simulated side impact crash tests showed similar reaction and deformation force values for both drawn parts and confirmed the same safety of B-pillar reinforcements made of tailor-welded blank as for the one made of simple blank.