Weiming Zhang

Influence of adding strong-carbide-formation elements multiply on particle-reinforced Fe-matrix composite layer produced by laser cladding

In the research hotspot of particle reinforced metal-matrix composite layer produced by laser cladding, in-situ reinforced particles obtained by adding strong-carbide-formation elements into cladding power have been attracting more attention for their unique advantage. The research has demonstrated that when adding strong-carbide-formation elements-Ti into the cladding powder of the Fe-C-Si-B separately, by optimizing the composition, better cladding coating with the characters of better strength and toughness, higher wear resistance and free of cracks. When the microstructure of cladding coating is hypoeutectic microstructure, its comprehensive performance is best. The research discovered that, compositely adding the strong-carbide-formation elements like Ti+V, Ti+Zr or V+Zr into the cladding coating is able to improve its comprehensive capability. All the cladding coatings obtained are hypoeutectic microstructure. The cladding coatings have a great deal of particulates, and its average microhardness reaches HV0.2700-1400. The research also discovered that the cladding coating obtained is of less cracking after adding the Ti+Zr.

Laser producing particulate reinforced Fe-based MMC coatings and industrial applications

This paper presents the research achievements on Fe-based metal matrix composite coatings (MMC) on steel and iron substrates by laser alloying and laser cladding and their industrial applications. The high carbon-equivalent design ensures the good formability and high hardness while eliminates hot cracking during rapid solidification. The jointly adding of strong-carbide-formation-elements promotes the precipitation of large quantity of hard particles. The typical microstructure of the MMC coating characterizes about 4000∼5000/mm2 carbide particles (1∼3 micron in diameter) homogeneously precipitated on iron-base matrix. The average hardness of the coating reaches up to Hv0.2 950∼1050. Tribological test proved that this particulate reinforced Fe-based MMC coating posses excellent wear resistance and couple ability with various different frictional counterparts as well as remarkable decrease of the friction coefficient. Its grain-abrasion resistance is better than that of the plasma sprayed Mo coating and its adhesive-abrasion resistance better than the chromium coating. This MMC coating also demonstrated unique corrosion resistance and contact-fatigue resistance. This particulate reinforced MMC coatings have been successfully applied in rock arms, cam shafts, piston rings of engine, plunger pistons and kerf of cutting knives.This paper presents the research achievements on Fe-based metal matrix composite coatings (MMC) on steel and iron substrates by laser alloying and laser cladding and their industrial applications. The high carbon-equivalent design ensures the good formability and high hardness while eliminates hot cracking during rapid solidification. The jointly adding of strong-carbide-formation-elements promotes the precipitation of large quantity of hard particles. The typical microstructure of the MMC coating characterizes about 4000∼5000/mm2 carbide particles (1∼3 micron in diameter) homogeneously precipitated on iron-base matrix. The average hardness of the coating reaches up to Hv0.2 950∼1050. Tribological test proved that this particulate reinforced Fe-based MMC coating posses excellent wear resistance and couple ability with various different frictional counterparts as well as remarkable decrease of the friction coefficient. Its grain-abrasion resistance is better than that of the plasma sprayed Mo coating and i...

Al1.3FeCoNiCuCr HEA coatings produced by laser cladding

The Al1.3FeCoNiCuCr HEA coatings are produced by pre-placed laser cladding on 45steel substrate. The influence of processing parameters on the crack formation of the HEA coatings is inves tigated, so is the influence of the content of so me other elements. The experiments results showed that: The microstructure of the Al1.3FeCoNiCuCr is composed of dendrite and inter-dendrite. The microstructure consists of only fcc and bcc phases. The crack density of the Al1.3FeCoNiCuCr HEA coatings is 0.533mm/mm2 when the parameter is 3000W and 350mm/min. It decreases to 0.464mm/mm2 when the parameter changes to 3500W and 250mm/min. In both cases, the cracks run throughout the surface of the coating with the slag inclusion adhesion. On the other hand, with a 2wt.% addition of RE2O3 to the Al1.3FeCoNiCuCr HEA, the crack density decreases to 0.433mm/mm2. Furthermore, the throughout crack disappear and there only have some micro cracks in the interior of the coatings.

Microstructure and corrosion resistance of laser alloying coating in-situ synthesized on ductile iron

Laser produced composite coating reinforced by in-situ particles has been proved to have a lot of benefits for industrial application, owing to its high wear resistance, corrosion resistance, high temperature characteristics, etc. Fabricate in-situ particle reinforced coating on ductile iron by laser could be a good way to increase valve’s service life, and it is a promising application in the manufacturing industry. In this study, large-area composite coatings reinforced by in-situ particles with high nickel content were produced on ductile iron QT450-10 by laser alloying. The results reveal that the coatings have high cracking tendency, due to the high carbon content of the molten pool produced by laser beam. Vary the content of graphite and rare earth oxide in the alloying powders, and investigate the effect on the coatings’ cracking tendency. Meanwhile, change the laser processing method by conducting laser remelting treatment on the substrate previously, aiming to melting the spheroidal graphite prior to the laser alloying treatment. The effects on crack density of the alloying coatings are investigated. Besides, the influence of different alloying powder composition and laser processing method on the coatings’ microstructure, microhardness and corrosion resistance, which is revealed by electrochemistry experiments, is also discussed.Laser produced composite coating reinforced by in-situ particles has been proved to have a lot of benefits for industrial application, owing to its high wear resistance, corrosion resistance, high temperature characteristics, etc. Fabricate in-situ particle reinforced coating on ductile iron by laser could be a good way to increase valve’s service life, and it is a promising application in the manufacturing industry. In this study, large-area composite coatings reinforced by in-situ particles with high nickel content were produced on ductile iron QT450-10 by laser alloying. The results reveal that the coatings have high cracking tendency, due to the high carbon content of the molten pool produced by laser beam. Vary the content of graphite and rare earth oxide in the alloying powders, and investigate the effect on the coatings’ cracking tendency. Meanwhile, change the laser processing method by conducting laser remelting treatment on the substrate previously, aiming to melting the spheroidal graphite prio...

Effects of rare earth oxide on the nucleation of carbide particles in laser cladded MMCp coating

Particulate reinforced metal matrix composite (MMCp) has excellent properties such as good wear resistance, corrosion resistance and high temperature properties. Various volume fractions of ceramic particles are usually deposited onto the metal surface to form MMC with improved performances by laser cladding. Recent literatures show that laser melting powders containing carbide-formation elements and carbon, is favorable for the formation of in situ synthesized carbide particles in MMC.Researches approve that the rare earth oxide (RExOy) plays a very important role in the precipitating of the in situ synthesized carbide particles especially as a heterogeneous nucleus of the carbides, which will greatly increase the distributing density of the enhanced particles. RExOy is commonly used to increase the laser absorptivity of the coating powder, to decrease the activity and improve the solubility of the alloy elements in the laser melt. At present, many researches have been made on the refinement of crystal grain by adding RExOy. However, nearly few have been reported on the accelerating of nucleation of the reinforcement particles as heterogeneous nuclei, especially in the field of laser producing MMCp.By the observation and analysis of SEM, EDS and TEM, it is found that in the precipitating of the carbide particles, some of the RExOy are partially dissolved, while the other ones change into rare earth carbides. However, both of them act as heterogeneous nuclei for the forming of particles. A clear interface between the nucleus and periphery of the particle can be observed by SEM after etching due to their differences in composition and structure. After deeply etched, the nuclei may be completely eroded and then left holes.Particulate reinforced metal matrix composite (MMCp) has excellent properties such as good wear resistance, corrosion resistance and high temperature properties. Various volume fractions of ceramic particles are usually deposited onto the metal surface to form MMC with improved performances by laser cladding. Recent literatures show that laser melting powders containing carbide-formation elements and carbon, is favorable for the formation of in situ synthesized carbide particles in MMC.Researches approve that the rare earth oxide (RExOy) plays a very important role in the precipitating of the in situ synthesized carbide particles especially as a heterogeneous nucleus of the carbides, which will greatly increase the distributing density of the enhanced particles. RExOy is commonly used to increase the laser absorptivity of the coating powder, to decrease the activity and improve the solubility of the alloy elements in the laser melt. At present, many researches have been made on the refinement of crystal g...

Laser producing Ni-matrix composite reinforced by in-situ synthesized particles

Nickel base superalloy has been widely used in key parts in aerospace field for its excellent heat resistance and wear resistance, but some problems always occur in laser cladding layer produced directly with different commerce nickel base superalloy powder as cladding powder, such as lower hardness or bad formation accompanying with higher hardness.The concept on producing Fe-matrix in-situ synthesized particles reinforced composite coatings by means of energy fluctuation and concentration fluctuation in melt by jointly adding of multi strong-carbide-formation elements and carbon is used in laser producing Ni-matrix composite. By adding strong-carbide-formation elements Ti, Zr, W and C into Inconel 625 powder, Ni-matrix composite reinforced by in-situ synthesized particles can be produced by laser cladding or laser alloying, without pores and cracks. The microstructure of the composite characterizes the dispersive and homogeneous precipitation of about 104/mm2 particles in micron size distributed homogeneously on γ-Ni dendritic. The average micohardness of the composite is above HV0.2400. EDAS analysis indicates that there are some proportions of strong-carbide-formation elements Ti, Zr, Nb, Mo, W and C in the particles, so they can be called as complex carbide.The influence of C content and W content in powder joined is specially discussed about.Nickel base superalloy has been widely used in key parts in aerospace field for its excellent heat resistance and wear resistance, but some problems always occur in laser cladding layer produced directly with different commerce nickel base superalloy powder as cladding powder, such as lower hardness or bad formation accompanying with higher hardness.The concept on producing Fe-matrix in-situ synthesized particles reinforced composite coatings by means of energy fluctuation and concentration fluctuation in melt by jointly adding of multi strong-carbide-formation elements and carbon is used in laser producing Ni-matrix composite. By adding strong-carbide-formation elements Ti, Zr, W and C into Inconel 625 powder, Ni-matrix composite reinforced by in-situ synthesized particles can be produced by laser cladding or laser alloying, without pores and cracks. The microstructure of the composite characterizes the dispersive and homogeneous precipitation of about 104/mm2 particles in micron size distributed homogen...

Formation of micro-nano structure by laser deposition and dealloying of copper alloy layer on macro-component surface

Nano-alloys or nano-structure often display novel physical, chemical and mechanical properties. It is of great scientific and engineering meanings to deposit micro-nano structure on macro-component surface to locally achieve nano-properties for potential applications. Laser deposition offers a promising approach to deposit a designed structure with designed composition on any location of a component.This paper focuses on the formation of micro-nano porous structure by laser deposition and dealloying of copper alloy layer on macro-component surface. A MnxCu1-x powder mixture was laser deposited on steel substrates to obtain layers with exact composition by laser processing optimization and original power composition optimization. These layers were then dealloyed in electrolyte by both free corrosion and electrochemical etching of manganese component. Bicontinuous porous copper layer with porosity in size of about 700u2005nm was formed after electrochemical etching, while no porous copper layer could be obtained in free corrosion. Dilute ratio, chemical composition and microstructure of the alloy layers were investigated using SEM, X-EDS and XRD. The results indicate that porous copper layer could be obtained by integrating laser deposition with low dilute ratio and electrochemical dealloying.Nano-alloys or nano-structure often display novel physical, chemical and mechanical properties. It is of great scientific and engineering meanings to deposit micro-nano structure on macro-component surface to locally achieve nano-properties for potential applications. Laser deposition offers a promising approach to deposit a designed structure with designed composition on any location of a component.This paper focuses on the formation of micro-nano porous structure by laser deposition and dealloying of copper alloy layer on macro-component surface. A MnxCu1-x powder mixture was laser deposited on steel substrates to obtain layers with exact composition by laser processing optimization and original power composition optimization. These layers were then dealloyed in electrolyte by both free corrosion and electrochemical etching of manganese component. Bicontinuous porous copper layer with porosity in size of about 700u2005nm was formed after electrochemical etching, while no porous copper layer could be obtaine...

Precipitating behavior of in situ synthesized multiple carbide particles in laser cladded MMC coating

Metal matrix composite (MMC) has attracted extensive investigation in material science and engineering due to its excellent properties such as good wear resistance, corrosion resistance and high temperature properties. Recent literatures show increased interests in laser cladded MMC coatings containing various volume fractions of ceramic particles. Our previous research approves that laser melting high-carbon-equivalent powders containing strong-carbide-formation elements (SCFEs) such as Ti, Zr, Nb and V, is favorable for the formation of dispersed, homogeneous and in situ synthesized carbide particles in melt. The particles reinforcement MMC coating displays excellent wearability and good combination of strength and toughness, which has been successfully applied in industrial applications. It is revealed that two or more SCFEs have significant effects on the in situ precipitation of multiple carbide particles and distribution. However, the formation mechanism of the in situ multiple carbide particles was not clearly up to date. This paper focuses on the morphology characteristics and precipitating behavior of the multiple carbides.The results show that the microstructure of the coatings is typical metastable hypo-eutectic, consisting of twin martensite (M), cementite (Fe3C), residual austenite (γ’) and dispersed in situ synthesized carbide particles. EDS and TEM analyses indicate that the particles are multiple carbides with peritectic structures, indicating their nucleation and growth process. During the in situ precipitation of the multiple carbides, zirconium and titanium play a key role in promoting the nucleation of the particles. ZrC precipitates before TiC, while TiC before WC. The study also shows that Ti is the strongest carbide-formation element.Metal matrix composite (MMC) has attracted extensive investigation in material science and engineering due to its excellent properties such as good wear resistance, corrosion resistance and high temperature properties. Recent literatures show increased interests in laser cladded MMC coatings containing various volume fractions of ceramic particles. Our previous research approves that laser melting high-carbon-equivalent powders containing strong-carbide-formation elements (SCFEs) such as Ti, Zr, Nb and V, is favorable for the formation of dispersed, homogeneous and in situ synthesized carbide particles in melt. The particles reinforcement MMC coating displays excellent wearability and good combination of strength and toughness, which has been successfully applied in industrial applications. It is revealed that two or more SCFEs have significant effects on the in situ precipitation of multiple carbide particles and distribution. However, the formation mechanism of the in situ multiple carbide particles was...

Laser strengthening of air-cooled diesel engine phosphorus cast iron cylinder liner and its friction & wear properties

This paper presents the research on laser hardening of phosphorus cast iron cylinder liner for air-cooled diesel engine. The microstructure, microhardness, friction and wear properties of the strengthened layers were investigated. The research results indicate that laser surface melting treatment results in the disappearance of strengthening phase phosphide eutectic, which deteriorates the property of the phosphorus cast iron. Laser transformation hardening can improve the property of phosphide eutectic. In some processing conditions, the phosphide eutectics remelt and crystallize into a fine structure, and some binary phosphide eutectics convert into ternary. Tribological tests indicate that the reservation of the original phosphide eutectic and the morphology of the phosphide eutectic after laser hardening have significant influences on the friction & wear properties of phosphorus cast iron cylinder liner.This paper presents the research on laser hardening of phosphorus cast iron cylinder liner for air-cooled diesel engine. The microstructure, microhardness, friction and wear properties of the strengthened layers were investigated. The research results indicate that laser surface melting treatment results in the disappearance of strengthening phase phosphide eutectic, which deteriorates the property of the phosphorus cast iron. Laser transformation hardening can improve the property of phosphide eutectic. In some processing conditions, the phosphide eutectics remelt and crystallize into a fine structure, and some binary phosphide eutectics convert into ternary. Tribological tests indicate that the reservation of the original phosphide eutectic and the morphology of the phosphide eutectic after laser hardening have significant influences on the friction & wear properties of phosphorus cast iron cylinder liner.

Influence of processing technique on practical large area metal-matrix composite coating produced by laser cladding

Laser cladding has been attracting a great deal of researches in the past years, however, cracking evolved in laser cladding for large area coatings limits its practical industrial applications. A FeCSiB base metal matrix composite coating reinforced by carbide particles can be a good way to suppress cracking, since such a coating is composed of tough hypoeutectic FeCSiB matrix and dispersively distributed WC, TiC hard particles, which can ensure the good toughness of the cladded coating to endure the tensile stress induced in laser cladding.In order to further eliminate cracks in large area cladding, the influence of processing techniques on cracking tendency on particulate reinforced metal-matrix composite coating was investigated in this paper. By introducing a method with reversed pre-deformation, preheating and postheating treatment at 450℃, large area clad coatings with optimized FeCSiB+Ti+Zr alloy powder on 12Cr2Ni4A component were achieved with smooth surface, low deformation and free of cracks un...