Materials Performance and Characterization, Sep 19, 2017
This paper investigates an application of ultrasonic stirring in water and oil-immersion quenchin... more This paper investigates an application of ultrasonic stirring in water and oil-immersion quenching of a medium carbon steel sample. By developing a pressure acoustic simulation, the distribution of ultrasound pressure and acceleration in quenching media was predicted. By using the standard temperature probe of Inconel 600, the cooling curves of water and quench oil were recorded with and without ultrasound agitation. Using the same conditions, a quenching of the steel cylinders made for carbon steel C45 was performed. The experimental results have shown a significant impact of ultrasound agitation on cooling curve parameters, sample distortions, and surface hardness distribution and its hardenability.
U radu se razmatra uspjesnost zamjene starih međupolnih potpora hidrogeneratorskog rotora izrađen... more U radu se razmatra uspjesnost zamjene starih međupolnih potpora hidrogeneratorskog rotora izrađenih od slitine P.AlZn5Mg1Cr, podložnih cestim lomovima i pukotinama, potporama izrađenim od precipitacijski ocvrstive slitine P.AlSi7Mg wa. Analizirana su postignuta mehanicka svojstva i mikrostruktura slitine P.AlSi7Mg wa nakon otapajuceg žarenja i umjetnog dozrijevanja, te su opisani su kriteriji za njeno usvajanje u proizvodnji hidrogeneratora.
U radu je opisan postupak povrsinskog otvrdnjavanja indukcijskom kaljenjem. Za precizno definiran... more U radu je opisan postupak povrsinskog otvrdnjavanja indukcijskom kaljenjem. Za precizno definiranje radnih parametara ovog postupka preporu6ena je primjena njegove racunalne simulacije. U radu su analizirani glavni fizikalni procesi koji određuju povrsinsku tvrdocu, dubinu kaljenja, oblik zakaljene zone i njenu otpornost na trosenje. Opisane su analiticke i numericke metode za rjesavanje matematickih modela simulacije indukcijskog kaljenja. Postavljena je energetska bilanca procesa i razrađeni su matematicki modeli elektromagnetskih, termodinamickih i mikrostrukturnih procesa u obradku tijekom indukcijskog kaljenja. Ovi matematicki modeli povezani su simulacijskim algoritmom i rijeseni vlastito razvijenim racunalnim programom pomocu metode rubnih elemenata (za matematicki model elektromagnetskih procesa) i metode konacnih elemenata (za matematicki model termodinamickih procesa). Uz simulacijski program razvijena je i baza podataka sa svojstvima indukcijski kaljenih materijala: toplinskim, elektri6nim i magnetskim, ovisnim o temperaturi. Predloženi program provjeren je na primjerima indukcijskog kaljenja valjaka dimenzija 020x95 mm od celika t4?32. Izmjerene vrijednosti povrsinske tvrdoce i dubine kaljenja valjaka uspoređene su sa zadanim iznosima prema kojima je provedena racunalna simulacija, to je ustanovljena dobra podudarnost simulacijskih i postignutih rezultata. Zakljucuje se da su nužne daljnje provjere i usavrsavanje simulacijskog programa za osnosimetri6ne obradke složenijih oblika i razlicite vrste celika za poboljsavanje.
This paper investigates the effect of the addition of 0.2 g/L of TiO2 nanoparticles in water on d... more This paper investigates the effect of the addition of 0.2 g/L of TiO2 nanoparticles in water on deformation cylinder with the length of 66 mm and a diameter of 12.5 mm made of steel EN 90MnCrV8. Experiments were conducted with vertical cylinder immersion into the water or nanofluid, with and without agitation. Cooling curve of tested quench media are recorded by the ivf SmartQuench system and it is analyzed in the computer program ivf SQintegraver4.0TM in aim to determine cooling parameters and the heat transfer coefficient (HTC). The HTC was used in a finite element (FE) simulation of deformation in quenched cylinders. The diameter of cylinders was measured over cylinder’s height and compared with the results of FE simulations. The measured change in diameter over cylinder’s height showed significant dependence of deformation from cooling conditions and the quenchant used.
Materials Performance and Characterization, Jun 18, 2014
Predicting thermal distortions and residual stresses after steel heat treatment is a complex task... more Predicting thermal distortions and residual stresses after steel heat treatment is a complex task in which the solution involves the use of a number of process parameters and nonlinear variation of steel properties. Former investigations in transformation-free cooling processes of long cylindrical work pieces in a gas nozzle field showed a typical behavior of the dimensional changes which indicated the possibility of introducing dimensionless numbers to predict thermal distortions. It was found that the changes in the dimensions of cylinders correlate well with only a few dimensionless numbers which are defined as function of shape and dimensions of components, its initial temperature, temperature of the quenching media, heat transfer coefficient, heat conductivity, heat capacity, density, thermal expansion coefficient, Young's modulus, Poisson's ratio, yield strength, and strain hardening behavior. For a systematic investigation of impacts on dimensional changes and residual stresses after transformation-free cooling, a representative group of 28 austenitic stainless steels was selected from literature. Their properties were statistically analyzed and three representative combinations of steel properties have been selected. The numerical simulations were carried out by use of the commercial finite element (FE) program SYSWELD 2005 with the aim to predict residual stresses and change of dimensions of a long cylinder made of austenitic stainless steel after gas cooling from the high temperature down to room temperature. The FE results were analyzed with the nonlinear regression methods and with genetic programming methods. From these analyses, two dimensionless mathematical models were proposed, one for prediction of thermal distortions and the other for prediction of equivalent residual stresses. The proposed dimensionless regression models allow the portability of the calculation results to similar cooling conditions (temperature independent heat transfer) for a transformation-free cooling of long cylinders made from any austenitic steel selected from the considered representative group of steels.
Former investigations in transformation-free cooling processes of long cylindrical workpieces in ... more Former investigations in transformation-free cooling processes of long cylindrical workpieces in a gas nozzle field showed a typical behaviour of the dimensional changes, which correlated to only few dimensionless numbers. These numbers are created by the following parameters: shape and dimensions of component, its initial temperature, temperature of the quenching media, heat transfer coefficient, heat conductivity, heat capacity, density, thermal expansion coefficient, Young’ s modulus, Poisson’ s ratio, yield strength and strain hardening behaviour. The representative group of 28 austenitic stainless steels was selected from literature. Their properties were statistically analyzed in order to carry out a systematic investigation of the most significant material properties and process parameters of dimension and shape changes during transformation-free cooling. The characteristic values of statistically significant interval of considered austenitic steel properties – average and standard deviation - as well as the range of usual process parameters for their heat treatment are used for simulations execution by the commercial FEM program SYSWELD. The relative changes of the component dimensions obtained from numerical simulations, have been analyzed in dependence of six autonomous dimensionless numbers with their interactions in order to find the proper equations for prediction of unavoidable distortion in a transformation-free cooling. To define these equations, the method of nonlinear regression analysis was used.
Materials Performance and Characterization, May 8, 2014
Quenching Research Centre (QRC) was established at the beginning of 2010 through the financial su... more Quenching Research Centre (QRC) was established at the beginning of 2010 through the financial support for excellence of the Ministry of Science Education and Sport, of the Republic of Croatia. The main investigation and research possibilities and potentials of the QRC are: quenching in liquids or in a salt bath and cooling by high pressure gases. As a result of long term research, the Temperature Gradient System has been designed, together with a unique cylindrical probe of 50 mm diameter by 200 mm instrumented with three thermocouples. Another device used at the Centre was the IVFSmartQuench® system according to ISO 9950, using a quenching device with agitation according to the ASTM D6482 standard. That equipment is used to investigate liquid quenchants and process parameters, including development of new quenchants: water, oil, and polymer based nanofluids, agitated by ultrasonic vibrations as a novel technology. QRC is also equipped with unique high pressure gas quenching facilities, providing the hardware for controllable heat extraction. The aim of using that equipment is to develop the method for measuring hardenability of high-alloyed steels when they are gas quenched and where a Jominy test is not applicable. QRC is also one of the initiators and an active participant in the project Global database on cooling intensities of liquid quenchants, which is coordinated and conducted by International Federation for Heat Treatment and Surface Engineering (IFHTSE).
Materials Performance and Characterization, Sep 19, 2017
Titanium-based hard coatings are known for increasing both hot work and cold work tool steel perf... more Titanium-based hard coatings are known for increasing both hot work and cold work tool steel performance in terms of wear and corrosion resistance. In this paper, the influence of different steel substrates on the properties of plasma-assisted chemical vapor deposition (PACVD) gradient multilayer titanium carbo-nitride (TiCN) coating was investigated. The same gradient multilayer TiCN coating was deposited by pulsed direct current (dc) PACVD on a hot work tool steel grade X37CrMoV5-1 and two Bohler cold work tool steels K390 PM and K110. Hardened samples of each steel were also included in the investigation. The coating-substrate systems have been characterized with respect to their chemical composition, thickness, adhesion, and resistance to electrochemical corrosion, abrasion, erosion, and dry sliding wear. The results show an increased wear and corrosion resistance of TiCN-coated specimens compared with noncoated and prehardened specimens. The application of gradient multilayer TiCN coating on different steel substrates shows the different behavior of TiCN coating. Therefore, besides the coating itself, the base material on which the coating is applied has a significant influence on the tool properties.
Materials Performance and Characterization, Sep 11, 2017
This paper investigates the abrasion and erosion wear resistance of the multilayer coating within... more This paper investigates the abrasion and erosion wear resistance of the multilayer coating within the system Ti-B-N applied to samples made of two hardened and tempered tool steels: Bohler grades K390 MC and X155CrVMo12-1. The multilayer coating consists from the thin interlayer TiN deposited directly on steel substrate and the Ti(B,N) coating, with continuous variation of stoichiometric ratio of boron and nitrogen through the thickness of the coating. Near the TiN interlayer Ti(B,N) coating has only a small content of boron while at the surface the layer TiB2 has been obtained. The multilayer TiN/Ti(B,N) coating was produced by the direct current plasma-assisted chemical vapor deposition (dc PACVD) in an industrial furnace with a hot wall. Tests of abrasive wear resistance were performed using an abrasive wear testing machine constructed according to ASTM G65-15, Standard Test Method for Measuring Abrasion Using the Dry Sand/Rubber Wheel Apparatus. The weight loss of samples was measured after a total wear path of 358 m. The test of erosion resistance was carried out by exposing the samples to impact erosion of fine sand particles and by determining the weight loss after 60 min of wear. Worn surfaces were analyzed by scanning electron microscopy (SEM). The results show a significant improvement in the abrasion and the erosion wear resistance of the TiN/Ti(B,N) coating applied to both tool steel samples with compared with the noncoated samples.
U radu su prikazani vlastiti rezultati ispitivanja utjecaja na otpornost na adhezijsko trosenje i... more U radu su prikazani vlastiti rezultati ispitivanja utjecaja na otpornost na adhezijsko trosenje i koroziju ugljicnog celika C45 nakon postupaka nitrokarburiranja sa i bez naknadne oksidacije u solnoj kupci, boriranja u pasti i vanadiranja u solnoj kupci.. Na uzorcima je ispitana hrapavost povrsine, mikrostruktura rubnog sloja, te su provedena ispitivanja otpornosti na adhezijsko trosenje i otpornosti na koroziju. Dobiveni rezultati pokazali su dobru otpornost na koroziju i adhezijsko trosenje nitrokarburiranog i naknadno oksidiranog, te boriranog sloja. Vanadirani uzorci pokazali su sklonost pitting koroziji.
U rada su ukratko opisani najznacajniji postupci povrsinskog kaljenja odljevaka od sivog i nodula... more U rada su ukratko opisani najznacajniji postupci povrsinskog kaljenja odljevaka od sivog i nodularnog lijeva kojima se bitno povisuje otpornost na trosenje. Prikazani su nacini pravilnog oznacavanja zahtijeva za lokalnim povrsinskim kaljenjem na crtežima. Uz uvjete zakaljivosti, navedene su tipicne vrste sivih i nodularnih ljevova prikladnih za povrsinsko kaljenje. Opisani su i prikazani rezultati odgovarajucih postupaka korekcijske toplinske obrade, prije ili u sklopu povrsinskog kaljenja, kojima je moguce na nekaljivim ljevovima postici dobru zakaljivost. Primjenom takvih postupaka postiže se povisena otpornost na trosenje uz zadržavanje povoljnih svojstava jezgre.
Materials Performance and Characterization, Sep 19, 2017
This paper investigates an application of ultrasonic stirring in water and oil-immersion quenchin... more This paper investigates an application of ultrasonic stirring in water and oil-immersion quenching of a medium carbon steel sample. By developing a pressure acoustic simulation, the distribution of ultrasound pressure and acceleration in quenching media was predicted. By using the standard temperature probe of Inconel 600, the cooling curves of water and quench oil were recorded with and without ultrasound agitation. Using the same conditions, a quenching of the steel cylinders made for carbon steel C45 was performed. The experimental results have shown a significant impact of ultrasound agitation on cooling curve parameters, sample distortions, and surface hardness distribution and its hardenability.
U radu se razmatra uspjesnost zamjene starih međupolnih potpora hidrogeneratorskog rotora izrađen... more U radu se razmatra uspjesnost zamjene starih međupolnih potpora hidrogeneratorskog rotora izrađenih od slitine P.AlZn5Mg1Cr, podložnih cestim lomovima i pukotinama, potporama izrađenim od precipitacijski ocvrstive slitine P.AlSi7Mg wa. Analizirana su postignuta mehanicka svojstva i mikrostruktura slitine P.AlSi7Mg wa nakon otapajuceg žarenja i umjetnog dozrijevanja, te su opisani su kriteriji za njeno usvajanje u proizvodnji hidrogeneratora.
U radu je opisan postupak povrsinskog otvrdnjavanja indukcijskom kaljenjem. Za precizno definiran... more U radu je opisan postupak povrsinskog otvrdnjavanja indukcijskom kaljenjem. Za precizno definiranje radnih parametara ovog postupka preporu6ena je primjena njegove racunalne simulacije. U radu su analizirani glavni fizikalni procesi koji određuju povrsinsku tvrdocu, dubinu kaljenja, oblik zakaljene zone i njenu otpornost na trosenje. Opisane su analiticke i numericke metode za rjesavanje matematickih modela simulacije indukcijskog kaljenja. Postavljena je energetska bilanca procesa i razrađeni su matematicki modeli elektromagnetskih, termodinamickih i mikrostrukturnih procesa u obradku tijekom indukcijskog kaljenja. Ovi matematicki modeli povezani su simulacijskim algoritmom i rijeseni vlastito razvijenim racunalnim programom pomocu metode rubnih elemenata (za matematicki model elektromagnetskih procesa) i metode konacnih elemenata (za matematicki model termodinamickih procesa). Uz simulacijski program razvijena je i baza podataka sa svojstvima indukcijski kaljenih materijala: toplinskim, elektri6nim i magnetskim, ovisnim o temperaturi. Predloženi program provjeren je na primjerima indukcijskog kaljenja valjaka dimenzija 020x95 mm od celika t4?32. Izmjerene vrijednosti povrsinske tvrdoce i dubine kaljenja valjaka uspoređene su sa zadanim iznosima prema kojima je provedena racunalna simulacija, to je ustanovljena dobra podudarnost simulacijskih i postignutih rezultata. Zakljucuje se da su nužne daljnje provjere i usavrsavanje simulacijskog programa za osnosimetri6ne obradke složenijih oblika i razlicite vrste celika za poboljsavanje.
This paper investigates the effect of the addition of 0.2 g/L of TiO2 nanoparticles in water on d... more This paper investigates the effect of the addition of 0.2 g/L of TiO2 nanoparticles in water on deformation cylinder with the length of 66 mm and a diameter of 12.5 mm made of steel EN 90MnCrV8. Experiments were conducted with vertical cylinder immersion into the water or nanofluid, with and without agitation. Cooling curve of tested quench media are recorded by the ivf SmartQuench system and it is analyzed in the computer program ivf SQintegraver4.0TM in aim to determine cooling parameters and the heat transfer coefficient (HTC). The HTC was used in a finite element (FE) simulation of deformation in quenched cylinders. The diameter of cylinders was measured over cylinder’s height and compared with the results of FE simulations. The measured change in diameter over cylinder’s height showed significant dependence of deformation from cooling conditions and the quenchant used.
Materials Performance and Characterization, Jun 18, 2014
Predicting thermal distortions and residual stresses after steel heat treatment is a complex task... more Predicting thermal distortions and residual stresses after steel heat treatment is a complex task in which the solution involves the use of a number of process parameters and nonlinear variation of steel properties. Former investigations in transformation-free cooling processes of long cylindrical work pieces in a gas nozzle field showed a typical behavior of the dimensional changes which indicated the possibility of introducing dimensionless numbers to predict thermal distortions. It was found that the changes in the dimensions of cylinders correlate well with only a few dimensionless numbers which are defined as function of shape and dimensions of components, its initial temperature, temperature of the quenching media, heat transfer coefficient, heat conductivity, heat capacity, density, thermal expansion coefficient, Young's modulus, Poisson's ratio, yield strength, and strain hardening behavior. For a systematic investigation of impacts on dimensional changes and residual stresses after transformation-free cooling, a representative group of 28 austenitic stainless steels was selected from literature. Their properties were statistically analyzed and three representative combinations of steel properties have been selected. The numerical simulations were carried out by use of the commercial finite element (FE) program SYSWELD 2005 with the aim to predict residual stresses and change of dimensions of a long cylinder made of austenitic stainless steel after gas cooling from the high temperature down to room temperature. The FE results were analyzed with the nonlinear regression methods and with genetic programming methods. From these analyses, two dimensionless mathematical models were proposed, one for prediction of thermal distortions and the other for prediction of equivalent residual stresses. The proposed dimensionless regression models allow the portability of the calculation results to similar cooling conditions (temperature independent heat transfer) for a transformation-free cooling of long cylinders made from any austenitic steel selected from the considered representative group of steels.
Former investigations in transformation-free cooling processes of long cylindrical workpieces in ... more Former investigations in transformation-free cooling processes of long cylindrical workpieces in a gas nozzle field showed a typical behaviour of the dimensional changes, which correlated to only few dimensionless numbers. These numbers are created by the following parameters: shape and dimensions of component, its initial temperature, temperature of the quenching media, heat transfer coefficient, heat conductivity, heat capacity, density, thermal expansion coefficient, Young’ s modulus, Poisson’ s ratio, yield strength and strain hardening behaviour. The representative group of 28 austenitic stainless steels was selected from literature. Their properties were statistically analyzed in order to carry out a systematic investigation of the most significant material properties and process parameters of dimension and shape changes during transformation-free cooling. The characteristic values of statistically significant interval of considered austenitic steel properties – average and standard deviation - as well as the range of usual process parameters for their heat treatment are used for simulations execution by the commercial FEM program SYSWELD. The relative changes of the component dimensions obtained from numerical simulations, have been analyzed in dependence of six autonomous dimensionless numbers with their interactions in order to find the proper equations for prediction of unavoidable distortion in a transformation-free cooling. To define these equations, the method of nonlinear regression analysis was used.
Materials Performance and Characterization, May 8, 2014
Quenching Research Centre (QRC) was established at the beginning of 2010 through the financial su... more Quenching Research Centre (QRC) was established at the beginning of 2010 through the financial support for excellence of the Ministry of Science Education and Sport, of the Republic of Croatia. The main investigation and research possibilities and potentials of the QRC are: quenching in liquids or in a salt bath and cooling by high pressure gases. As a result of long term research, the Temperature Gradient System has been designed, together with a unique cylindrical probe of 50 mm diameter by 200 mm instrumented with three thermocouples. Another device used at the Centre was the IVFSmartQuench® system according to ISO 9950, using a quenching device with agitation according to the ASTM D6482 standard. That equipment is used to investigate liquid quenchants and process parameters, including development of new quenchants: water, oil, and polymer based nanofluids, agitated by ultrasonic vibrations as a novel technology. QRC is also equipped with unique high pressure gas quenching facilities, providing the hardware for controllable heat extraction. The aim of using that equipment is to develop the method for measuring hardenability of high-alloyed steels when they are gas quenched and where a Jominy test is not applicable. QRC is also one of the initiators and an active participant in the project Global database on cooling intensities of liquid quenchants, which is coordinated and conducted by International Federation for Heat Treatment and Surface Engineering (IFHTSE).
Materials Performance and Characterization, Sep 19, 2017
Titanium-based hard coatings are known for increasing both hot work and cold work tool steel perf... more Titanium-based hard coatings are known for increasing both hot work and cold work tool steel performance in terms of wear and corrosion resistance. In this paper, the influence of different steel substrates on the properties of plasma-assisted chemical vapor deposition (PACVD) gradient multilayer titanium carbo-nitride (TiCN) coating was investigated. The same gradient multilayer TiCN coating was deposited by pulsed direct current (dc) PACVD on a hot work tool steel grade X37CrMoV5-1 and two Bohler cold work tool steels K390 PM and K110. Hardened samples of each steel were also included in the investigation. The coating-substrate systems have been characterized with respect to their chemical composition, thickness, adhesion, and resistance to electrochemical corrosion, abrasion, erosion, and dry sliding wear. The results show an increased wear and corrosion resistance of TiCN-coated specimens compared with noncoated and prehardened specimens. The application of gradient multilayer TiCN coating on different steel substrates shows the different behavior of TiCN coating. Therefore, besides the coating itself, the base material on which the coating is applied has a significant influence on the tool properties.
Materials Performance and Characterization, Sep 11, 2017
This paper investigates the abrasion and erosion wear resistance of the multilayer coating within... more This paper investigates the abrasion and erosion wear resistance of the multilayer coating within the system Ti-B-N applied to samples made of two hardened and tempered tool steels: Bohler grades K390 MC and X155CrVMo12-1. The multilayer coating consists from the thin interlayer TiN deposited directly on steel substrate and the Ti(B,N) coating, with continuous variation of stoichiometric ratio of boron and nitrogen through the thickness of the coating. Near the TiN interlayer Ti(B,N) coating has only a small content of boron while at the surface the layer TiB2 has been obtained. The multilayer TiN/Ti(B,N) coating was produced by the direct current plasma-assisted chemical vapor deposition (dc PACVD) in an industrial furnace with a hot wall. Tests of abrasive wear resistance were performed using an abrasive wear testing machine constructed according to ASTM G65-15, Standard Test Method for Measuring Abrasion Using the Dry Sand/Rubber Wheel Apparatus. The weight loss of samples was measured after a total wear path of 358 m. The test of erosion resistance was carried out by exposing the samples to impact erosion of fine sand particles and by determining the weight loss after 60 min of wear. Worn surfaces were analyzed by scanning electron microscopy (SEM). The results show a significant improvement in the abrasion and the erosion wear resistance of the TiN/Ti(B,N) coating applied to both tool steel samples with compared with the noncoated samples.
U radu su prikazani vlastiti rezultati ispitivanja utjecaja na otpornost na adhezijsko trosenje i... more U radu su prikazani vlastiti rezultati ispitivanja utjecaja na otpornost na adhezijsko trosenje i koroziju ugljicnog celika C45 nakon postupaka nitrokarburiranja sa i bez naknadne oksidacije u solnoj kupci, boriranja u pasti i vanadiranja u solnoj kupci.. Na uzorcima je ispitana hrapavost povrsine, mikrostruktura rubnog sloja, te su provedena ispitivanja otpornosti na adhezijsko trosenje i otpornosti na koroziju. Dobiveni rezultati pokazali su dobru otpornost na koroziju i adhezijsko trosenje nitrokarburiranog i naknadno oksidiranog, te boriranog sloja. Vanadirani uzorci pokazali su sklonost pitting koroziji.
U rada su ukratko opisani najznacajniji postupci povrsinskog kaljenja odljevaka od sivog i nodula... more U rada su ukratko opisani najznacajniji postupci povrsinskog kaljenja odljevaka od sivog i nodularnog lijeva kojima se bitno povisuje otpornost na trosenje. Prikazani su nacini pravilnog oznacavanja zahtijeva za lokalnim povrsinskim kaljenjem na crtežima. Uz uvjete zakaljivosti, navedene su tipicne vrste sivih i nodularnih ljevova prikladnih za povrsinsko kaljenje. Opisani su i prikazani rezultati odgovarajucih postupaka korekcijske toplinske obrade, prije ili u sklopu povrsinskog kaljenja, kojima je moguce na nekaljivim ljevovima postici dobru zakaljivost. Primjenom takvih postupaka postiže se povisena otpornost na trosenje uz zadržavanje povoljnih svojstava jezgre.
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