Weldasearch® - sample results

Surface hardening

Copyright TWI (The Welding Institute) 2008

232873
Hardness improvement of surface alloyed materials fabricated with Fe based metamorphic powders by high energy electron beam irradiation.
NAM D H; LEE K; LEE S; KIM C P
Materials Science and Technology, vol.24, no.1. Jan.2008. pp.10-14. 5 fig., 1 tab., 15 ref.
[in English]

Surface alloyed materials were fabricated by depositing iron based metamorphic powders containing significant amounts of crystalline phases followed by irradiation with a high-energy electron beam, with a view to improving surface wear and thermal resistance properties; the microstructure and hardness properties of the surface alloyed material were evaluated. The powder was deposited onto carbon steel substrate (0.162%C, 1.06%Mn, 0.23%Si) and irradiated using one and two layer processes. The microstructure of the surface alloyed layer and room temperature and high temperature mechanical properties were investigated. The hardness properties are discussed with reference to the layer microstructure, particularly the presence of borides.

232579
Microstructures and properties of the nitrided layers fabricated on titanium substrate by direct current nitrogen arc melting technique.
LI X; REN Z N; SUN D Q; ZHAO Y Q; WANG L
China Welding, vol.17, no.1. Mar.2008. pp.18-22. 5 fig., 10 ref.
[in English]

Nitrided layers (TiN) were fabricated on commercially pure TA2 titanium substrate using a DC nitrogen arc melting method; the effects of arc current and arc travelling speed on the microstructure, hardness and wear resistance of the layers were investigated. Following nitriding, the microstructure and phase composition of the nitrided layers were analysed. Microhardness profiles through the layers were measured. Pin on disc abrasive wear tests were performed to determine wear resistance.

232614
Variable processing optic for laser beam hardening (Variable Bearbeitungsoptik zum Laserstrahlharten).
BONSS S; HANNWEBER J; KUHN S; SEIFERT M; BRENNER B; BEYER E
DVS Berichte, no.241. Laser Technology - New Developments and Applications. Proceedings, Conference, Jena, 23-24 Nov.2006. Publ: 40010 Dusseldorf, Germany; DVS-Verlag, for Deutscher Verband fur Schweissen und verwandte Verfahren; 2006. pp.95-100. 5 fig.
[in German]
[Also available on CD-ROM]

A laser beam forming system with scanner mirrors and adjustable beam spot width for the laser hardening of steel and cast iron materials using high-output diode lasers was developed (the "LASSY" system). The construction and functioning of the system are described. The system is equipped with focusing optics with a focal length of at least 300 mm. Two different temperature measuring systems for recording the surface temperature of the workpiece can be integrated - an analogue pyrometer and a camera-based system. Examples of the use of the system are presented: a demonstration piece showing a hardened track with variable width, and the hardening of a steam turbine blade.

231389
Causes of defects formed in steels and alloys in surface hardening using high power density heat sources.
SAMOTUGIN S S; MAZUR V A
Paton Welding Journal, no.3. Mar.2007. pp.23-26. 3 fig., 11 ref.
[in English; Russian]
(Translated from Avtomaticheskaya Svarka)

The causes and mitigation of defects in tool steels and cast iron subjected to high energy (0.1-10 MW/cm2) surface hardening by laser and plasma treatment are reviewed. Cracks in tool steel can arise from residual stresses associated with dissolution of the carbide phase. Residual stresses associated with incomplete dissolution of graphite can also cause cracking in grey cast iron. Cracking in both materials can be initiated by nonmetallic inclusions. Differences between laser and plasma treatment are observed when significant surface melting occurs, as the molten pool may be disturbed by the plasma jet. Defect formation is dependent upon the substrate composition and its initial microstructure. Cold cracking can occur whether the surface is melted or not, and is associated with stresses generated during treatment. Cracking may be prevented by modifying the heating cycle to reduce stress, and by tempering after hardening.

230385
Laser surface treatment for protection against wear.
MAN H C
In Book: Surface Coatings for Protection Against Wear. Ed: B.G.Mellor. Publ: Abington, Cambridge CB21 6AH, UK; Woodhead Publishing Ltd; 2006 and Boca Raton FL 33487, USA; CRC Press; 2006 on behalf of the Institute of Materials, Minerals & Mining. Chapter 10. pp.377-391. 5 fig., 1 tab., 23 ref.
[in English]

Laboratory results and industrial applications of laser surface engineering for enhancing the wear resistance of metallic components using high power infrared lasers are reviewed. Processes covered are laser transformation hardening, laser surface melting, laser surface alloying and laser surface cladding. In each case, the process mechanisms are described and some applications are mentioned. Suitable lasers are discussed briefly, comparing CO2 and Nd:YAG laser beam characteristics. The advantages and limitations of laser surface engineering are set out. Applications for laser surface engineering on steels, cast irons, aluminium alloys and titanium alloys are presented, including repair and new fabrication, with examples of treatment to enhance wear resistance and/or surface hardness and building up by surfacing.

228894
Fabrication of iron nitride coatings by reactive RF [radio frequency] plasma spraying.
YAMADA M; KOUZAKI Y; YASUI T; FUKUMOTO M
Surface and Coatings Technology, vol.201, no.3-4. 5 Oct.2006. pp.1745-1751. 11 fig., 3 tab., 25 ref.
[in English]
[See also Weldasearch 218555]

A reactive RF plasma spraying process using a water cooled substrate holder was investigated as a means of producing thick and dense iron nitride (Fe4N) based coatings; the effects of feedstock particle size, nitrogen flow rate and the addition of hydrogen on the nitridation and microstructure of the coatings were studied also. Conventional (particle size less than 75 microns) and fine (3-5 microns) feedstock powders were used; the particles were injected into an argon/nitrogen plasma (with and without hydrogen) and deposited onto carbon steel substrates. The microstructure of the coating, including nitride phase concentration, was examined and hardness properties were assessed.

227509
Residual stresses in tool steels after plasma hardening with melting of the surface.
SAMOTUGIN S S; MAZUR V A
Welding International, vol.21, no.1. 2007. pp.59-63. 2 fig., 2 tab., 17 ref.
[in English; Russian]
(Translation 3742) (Translated from Svarochnoe Proizvodstvo, vol.59, no.8. 2006. pp.20-26)

An investigation is presented into the residual stress distribution and solidification mechanism in 90KhF low-alloy tool steel and R6M5 high-speed tool steel after plasma hardening with surface melting. The tool steel specimens were treated with a high-power plasma jet under conditions corresponding to micromelting (molten layer depth up to 0.5 mm, surface relief unaffected) or macromelting (molten layer depth 22 mm, surface crater formation). Some R6M5 steel samples were subjected to additional volume tempering. Measurements were undertaken to determine residual stress distribution on transverse microsections, phase composition (martensite, retained austenite and carbide), Vickers hardness and fracture toughness. Solidification by dendritic and cellular mechanisms is discussed.

229587
Prediction of phase transformations during laser surface hardening of AISI 4140 including the effects of inhomogeneous austenite formation.
MIOKOVIC T; SCHULZE V; VOHRINGER O; LOHE D
Materials Science and Engineering A, vol.A435-436, no.5. Nov.2006. pp.547-555. 13 fig., 19 ref.
[in English]

Finite element based simulations (ABAQUS) were used to model local temperature changes and phase transformations during heating and cooling stages of the laser surface hardening of AISI 4140 steel. The simulations took into account the effect of inhomogeneous austenite formation. Dilatometric studies provided data for the material laws used in the simulations. The influence of heating and cooling rates was investigated also. The results were used to predict hardness profiles and were compared with experimental data.

229799
A quantitative analysis of the effect of laser transformation hardening on crack driving force in steels.
YANG B Q; ZHANG K; CHEN G N; LUO G X; XIAO J H
Surface and Coatings Technology, vol.201, no.6. 4 Dec.2006. pp.2208-2216. 10 fig., 3 tab., 31 ref.
[in English]

A mechanical model, based on small-scale-yielding linear elastic fracture mechanics theory, is developed to quantitatively analyse the effects of residual stress and hardness gradient during laser transformation hardening. Application of the Double Cantilever Beam model is discussed. The effects of residual stress and hardness gradient on crack driving force of the steels were quantified in terms of the J-integral. The relationship of the crack driving force to residual compressive stress and residual tensile stress is discussed.

229908
Laser transformation hardening of Ti-6Al-4V in solid state with accompanying kinetic model.
HAHN J D; SHIN Y C; KRANE M J M
Surface Engineering, vol.23, no.2. Mar.2007. pp.78-82. 6 fig., 1 tab., 12 ref.
[in English]

The influence of processing parameters on the diode laser transformation hardening of titanium alloy (Ti, 6%Al, 4%V) in the solid state was studied, and a kinetic model for the prediction of hardness profiles was developed. The variables were beam speed (0.5 or 2 mm/s) and beam energy (400-710 W). The specimens were sectioned and the Rockwell C hardness measured as a function of distance below the surface. A thermal model was used to calculate temperature distributions, and a kinetic model to predict alpha-to-beta transformation on heating, the proportion of martensitic alpha' formed on quenching, and hence the hardness.

228921
Modification of surface properties of 17-12-2 austenitic steel (Modyfikacja wlasnosci powierzchni ...).
ROZANSKI M
Biuletyn Instytutu Spawalnictwa, vol.50, no.2. 2006. pp.27-31. 7 fig., 6 tab., 12 ref.
[in Polish]

The article presents the results of investigations on nitriding, hardening and surfacing 17-12-2 type austenitic steel (17.5%Cr, 13%Ni, 2.7%Mo) to improve wear from erosion. The influence of manganese content in surfacing powder on the wear of overlays is given in a table. The erosion mechanism is discussed in the references. AISI 316 and AISI 1020 steels are specially noted.

226089
Models for diode laser transformation hardening of steels. Henry Granjon prize competition 2006 co-winner, Category A "Joining and fabrication technology" .
PANTSAR H; INTERNATIONAL INSTITUTE OF WELDING
Welding in the World, vol.50, no.9-10. Sept.-Oct.2006. pp.3-11. 14 fig., 1 tab., 17 ref.
[in English]
(IIW-1747-06 (ex doc.IV-910))

Two models for the diode laser transformation hardening process were developed; one for estimating the hardened depth and one for estimating the resulting hardness. Laser hardening experiments were carried out on low alloy steel (42CrMo4) and martensitic stainless steel (AISI 420L) materials to determine the effects of process parameters and oxidation on the absorptivity of the steel surfaces. The results were used to develop a model for estimating the hardened depth which was then experimentally validated. Hardening experiments were carried out on a range of seven steels to establish the phase transformations occurring during hardening. This information was used to develop a model to calculate the surface hardness using data from equilibrium diagrams. To validate the model the calculated hardness values were compared with measured hardness values for the seven steels and a further 34 commercial steel grades.

225739
Laser transformation hardening of a tool steel: simulation-based parameter optimisation and experimental results.
TOBAR M J; ALVAREZ C; AMADO J M; RAMIL A; SAAVEDRA E; YANEZ A
Surface and Coatings Technology, vol.200, no.22-23. 20 June 2006. pp.6362-6367. 6 fig., 1 tab., 14 ref.
[in English]

A three dimensional numerical model simulating the laser surface hardening process was developed; the model was used in a parametric analysis to optimise process parameters for the hardening of a hot work tool steel (AISI H13 stainless steel). The model uses both a three dimensional analytical model and a finite element based method to determine temperature distribution and history; this is used as input to a metallurgical phase transformation model based on the Johnson-Mehl-Avrami and Koistinen-Marburger equations. The parametric analysis was carried out and calculated hardness profiles were compared with experimental results.

224945
Laser hardening of castings of low- and medium-carbon steels.
SEMENTSEV A M
Welding International, vol.20, no.6. 2006. pp.491-495. 2 fig., 1 tab., 5 ref.
[in English; Russian]
(Translation 3649) (Translated from Svarochnoe Proizvodstvo, vol.59, no.1. 2006. pp.25-29)

An investigation is presented into the effect of laser irradiation on the microstructure, elemental distribution and mechanical properties of the low-carbon low-alloy cast steel 20GML and 35L cast carbon steel. A Kvant-15 pulsed periodic laser was used over a wide range of speeds and power densities on test pieces with or without an absorbing coating, resulting in treatment with and without surface melting. Characterisation of specimens consisted of metallographic examination, X-ray spectral microanalysis to determine elemental distributions, and microhardness measurements. Issues discussed include formation of martensite needles and ferrite grains, quenched structures in the zone of the laser effect, manganese redistribution, and the use of laser hardening to improve wear resistance of 35L steel buckets.

224061
Effects of the surface temperature and cooling rate on the residual stresses in a flame hardening of 12Cr steel.
LEE M K; KIM G H; KIM K H; KIM W W
Journal of Materials Processing Technology, vol.176, no.1-3. June 2006. pp.140-145.
[in English]

The residual stress properties generated by flame hardening in a low carbon 12%Cr steel, currently used as a nuclear steam turbine blade material, were examined with regard to surface temperature and cooling rate. The stresses were identified and related to phase transformation and contraction in the steel. The causes of cracks that initiated and propagated during the thermal cycling were established. The processing temperatures that resulted in suitable residual stresses and hardness were identified.

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