scholarly journals Improvement of Surface Properties of Inconel718 by HVOF Coating with WC-Metal Powder and by Laser Heat Treatment of the Coating

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Hui Gon Chun ◽  
Tong Yul Cho ◽  
Jae Hong Yoon ◽  
Gun Hwan Lee
Keyword(s):  
Heat Treatment ◽  
Wear Resistance ◽  
Corrosion Resistance ◽  
Metal Powder ◽  
Surface Properties ◽  
Porous Coating ◽  
Wear Depth ◽  
Laser Heat Treatment ◽  
Hvof Coating ◽  
Laser Heat

High-velocity oxygen-fuel (HVOF) thermal spray coating with WC-metal powder was carried out by using optimal coating process on an Inconel718 surface for improvement of the surface properties, friction, wear, and corrosion resistance. Binder metals such as Cr and Ni were completely melted and WC was decomposed partially to W2C and graphite during the high temperature (up to 3500°C) thermal spraying. The melted metals were bonded with WC and other carbides and were formed as WC-metal coating. The graphite and excessively sprayed oxygen formed carbon oxide gases, and these gases formed porous coating by evolution of the gases. The surface properties were improved by HVOF coating and were improved further by CO2laser heat treatment (LH). Wear resistance of In718 surface was improved by coating and LH at 25°C and an elevated temperature of 450°C, resulting in reduction of wear trace traces, and was further improved by LH of the coating in reducing wear depth. Corrosion resistance due to coating in sea water was improved by LH. HVOF coating of WC-metal powder on a metal surface and a LH of the coating were highly recommended for the improvement of In718 surface properties, the friction behavior, and wear resistance.

Wear and Corrosion Resistances of Inconel718, HVOF Coating of WC-Metal Powder and Laser Heat-Treated Coating

2013 ◽  
Vol 419 ◽  
pp. 381-387
Author(s):  
Hui Gon Chun ◽  
Yun Kon Joo ◽  
Jae Hong Yoon ◽  
Tong Yul Cho ◽  
Wei Fang ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Sea Water ◽  
Spray Coating ◽  
Porous Coating ◽  
Wear Depth ◽  
Laser Heat Treatment ◽  
Hvof Coating ◽  
Laser Heat ◽  
Wear And Corrosion ◽  
Heat Treated

For the Improvement of wear and corrosion resistances of Inconel718 (In718) surface, high velocity oxygen fuel (HVOF) thermal spray coating of micron-sized WC-Cr-C-Ni powder was coated onto Inconel718 surface and laser heat-treatment of the coating was carried out. Porous coating of porosity 2.2±0.4% was prepared by HVOF coating, and it was improved by laser heat-treatment, reducing the porosity to 0.35±0.08%. Micro-hardness of laser heat-treated coating increased more than four times compared to the surface of In718. Friction coefficient decreased by HVOF coating and laser heat-treatment. Wear resistance improved, decreasing the wear depth by the coating and laser heating. The interface between coating and In718 was compacted, and elements diffused from both coating and inconel718 substrate to interface, forming metal rich buffer zone (interface) and enhancing the adhesion of coating. Corrosion resistance improved by coating in sea water 3.5% NaCl solution and in 1M HCl acid, but it worsened in 1M NaOH base. For the improvement of wear and corrosion resistances of Inconel718, HVOF WC-metal power coating and laser heat-treatment are recommended.

Improving the Properties of Magnetic Bearing Shaft Material by HVOF Coating of WC-Metal Powder and Laser Heat Treatment

2012 ◽  
Vol 560-561 ◽  
pp. 1052-1058 ◽  
Author(s):  
T.Y. Cho ◽  
Y.K. Joo ◽  
J. H. Yoon ◽  
H. G. Chun ◽  
S.H. Zhang
Keyword(s):  
Heat Treatment ◽  
Metal Powder ◽  
Laser Heating ◽  
Surface Hardness ◽  
Magnetic Bearing ◽  
Free Carbon ◽  
Laser Heat Treatment ◽  
Friction Coefficients ◽  
Hvof Coating ◽  
Laser Heat

Abstract. Micron-sized WC-metal (WC-0.6%C-21%Cr-6%Ni) powder was coated onto the substrate of magnetic bearing shaft material Inconel718 (substrate or In718) using JK3500 HVOF thermal sprayer for the improvement of the surface properties of the substrate. The optimal coating process for the highest surface hardness was obtained using the Taguchi experimental program. The coating was laser heat-treated (LH) by CO2(g) laser for further improvement of the properties. During the thermal spraying, a small portion of metal carbides of powder decomposed to W2C, metals and free carbon. The free carbon reacted with excessively sprayed oxygen, and formed carbon oxide gases, forming porous coating. By laser-heating, porosity decreased and the porous strips at the interface of coating and substrate (coat/sub) compacted. At the interface, the precipitated graphite concentration decreased and the metal elements diffused from both the coating and substrate increased, enhancing the functions as buffer zone and increasing adhesion of coating. The surface hardness of substrate increased by coating and further increased by laser-heating from 410±30 Hv to 983±101 Hv and 1425±94 Hv respectively. Porosity of coating decreased by laser-heating from 2.6±0.4% to 0.35±0.06%, and coating thickness shrank from 280㎛ to 200㎛. Friction coefficients of substrate decreased from 0.52±0.02 to 0.36±0.04 by coating, because the free carbon formed by decomposition of WC to W2C functioned as a solid lubricant. By increasing sliding surface temperature from 25°C to 450°C, the friction coefficients of substrate and coating were decreased from 0.52±0.02 to 0.31±0.02 and from 0.36±0.04 to 0.23±0.04 respectively, because of easy formation of free carbon and metal oxides which functioned as solid lubricants. Wear depth of surface was decreased by coating and by LH coating from 55µm to 32 µm and to 12 µm respectively. HVOF coating of WC-metal powder on In718 surface and laser heat-treatment of the coating are highly recommended for the improvement of the properties of magnetic bearing shaft.

HVOF Coating of µ-WC-Metal Powder and Laser Heat-Treatment of the Coating for the Improvement of Turbo Shaft Material

2012 ◽  
Vol 586 ◽  
pp. 74-79
Author(s):  
T.Y. Cho ◽  
Y.K. Joo ◽  
J.H. Yoon ◽  
H.G. Chun ◽  
S.H. Zhang
Keyword(s):  
Heat Treatment ◽  
Metal Powder ◽  
Laser Heating ◽  
Wear Behavior ◽  
Substrate Surface ◽  
Surface Hardness ◽  
Thermal Spraying ◽  
Laser Heat Treatment ◽  
Hvof Coating ◽  
Laser Heat

A hybrid surface treatment was performed to improve the surface properties and the durability improvement of turbo shaft material Inconel718. A micron sized (µ) WC-metal powder (86% WC 10% Co 4% Cr) was coated onto a substrate surface using HVOF thermal spraying, and the coating was heat treated by a CO2 laser. With the HVOF coating of the powder onto the substrate, the surface hardness of substrate increased approximately 300% from 399 Hv to 1260±30 Hv, and further increase of approximately 40% from1260±30 Hv to 1820±100 Hv by laser heating the coating for 0.6 s. Porosity of coating decreased more than five times from 2.2±0.3% to 0.4±0.1% by laser heating. According to the reciprocating sliding test, friction and wear behavior of coating improved by coating for both sliding surface temperature of 25°C and 450°C. Therefore, the HVOF coating and laser heat treatment of coating are recommended for the durability improvement of turbo shaft materials.

The Effects of HVOF Coating of WC-CrC-Ni Powder on In718 and of CO2 Laser Heat Treatment on the Coating

2009 ◽  
Vol 54 (3) ◽  
pp. 1100-1103 ◽  
Author(s):  
Tong-Yul Cho ◽  
Jae-Hong Yoon ◽  
Yun-Kon Joo ◽  
Shihong- Zhang ◽  
Wei Fang ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Co2 Laser ◽  
Laser Heat Treatment ◽  
Hvof Coating ◽  
Laser Heat ◽  
Ni Powder

Study on Al Coating and Black Passive Film on Steel Surface

2013 ◽  
Vol 712-715 ◽  
pp. 403-406
Author(s):  
Li Yuan Niu ◽  
Yi Chang Su ◽  
Zi Mu Shi ◽  
Ji Xing Lin ◽  
Guang Yu Li
Keyword(s):  
Heat Treatment ◽  
Corrosion Resistance ◽  
Passive Film ◽  
Steel Surface ◽  
Zinc Coating ◽  
Laser Heat Treatment ◽  
Good Ductility ◽  
Binding Force ◽  
Laser Heat ◽  
Al Coating

An Al coating and black passive film technique was developed in this research. Meanwhile, a fine and uniform Al coating with good binding force on steel surface was prepared. And a black passive film was used as a post-treated film of the electroplated Al coating. The result proves that the corrosion resistance of electroplated Al coating was over one time higher than that of zinc coating by black passivation. Besides, Al coating was less brittle with good ductility and, it could be used as a pretreatment layer before conducting laser heat treatment to significantly improve the efficiency of laser heat treatment.

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