Surface Hardness Of Substrate Research Articles

Physical and Mechanical Properties of Twin-Wire Arc Spray and Wire Flame Spray Coating on Carbon Steel Surface

Thermal Spray Coating is a material surface engineering process, where the coating material is heated until it melts then the melt is pushed with high-pressure air as individual particles or droplets to a surface. This study compares two thermal spray coating methods, twin-wire arc spray and wire flame spray to measure the level of hardness, coating strength and good quality of the coating and porosity. This study used medium carbon steel AISI 1045 as substrate and coating material with FeCrMnNiCSiSP alloy elements (AISI 420). Testing mechanical properties were undergone by hardness testing and pull-off test to determine the coating's adhesive strength. The microstructures were observed using a microscope to test the physical properties. After analyzing the research results, it can be concluded that the twin-wire arc spray coating process produces an adequate level of hardness and coating strength. Twin-wire arc spray can increase the percentage value of substrate surface hardness by 50,56 % and the average coating strength of 21,345 MPa. The microstructure observation results on the coating show that the coating results from twin-wire arc spray have good coating quality with the bonds between the elements contained in the FeCrMnNiCSiSP wire which are bonded to each other and form layered layers and minimal porosity in the coating.

Enhancement of Ti-6Al-4V powder surface properties for cold spray deposition using fluidized Gas-Nitriding technique

Modification of Ti-6Al-4V powder surface was achieved by treating fluidized powder in N2 gas at 700 °C and 800 °C for hold times between 10 and 30 min. The technique is expected to lower surface oxygen content, and improve material properties such as flowability, resistance to moisture adsorption, etc. A relative increase in surface nitrogen content was observed with increasing reaction temperature and soak time. Analysis by X-ray photoelectron spectroscopy (XPS) indicated the removal of oxides, hydroxyl groups, and other oxygen species with an increase in the atomic N/O and Ti/O ratios at the surface. Gas-nitriding of Ti-6Al-4V at 700 °C and 800 °C for 30 min resulted in an increase of the surface N/O atomic ratio from 0.02 to 0.56 and 0.76, respectively. The surface reaction with nitrogen did not affect the bulk structure or morphology of the powder. This was evidenced by XRD results indicating that there was no bulk phase TiN present or any significant change in the d-spacing values for characteristic Ti-6Al-4V peaks. Additionally, there was no significant increase in surface hardness of substrates following the deposition of nitrided powders. Nitriding of Ti-6Al-4V improved powder performance during cold spray deposition by eliminating nozzle fouling and reducing porosity in deposited layers.

The effect of deposition parameters on structure, mechanical and adhesion properties of a-C:H on Ti6Al4V with gradient Ti-a-C:H:Ti interlayer

Diamond like carbon (DLC or a-C:H) is a coating material with broad application in many technical fields such as tribological, optical and biomedical applications. However, its outstanding mechanical and wear properties are counteracted by its poor adhesion to steel or titanium alloys. Therefore, to widen their usability in vast technological fields, the improvement and understanding of adhesion/cohesion of the DLC-metal substrate system is mandatory. In this study, a-C:H was deposited using a radio frequency magnetron plasma enhanced chemical vapor deposition (rf-magnetron-PECVD) process onto medical Ti Grade 23 (Ti6Al4V ELI) substrates, provided with a chemical gradient Ti-a-C:H:Ti interlayer. The deposition parameters, like Ar/C2H2 ratio and rf-power during gradient Ti-a-C:H:Ti interlayer deposition as well as working pressure and substrate bias voltage during the deposition of top a-C:H were varied. The layer systems mechanical and adhesion properties were characterized by nanoindentation and scratch testing. The samples microstructure after coating was examined by etching and SEM imaging. SEM cross sections revealed a columnar structure for gradient interlayer and amorphous structure for top a-C:H coating. The Ti-a-C:H:Ti-a-C:H coating system increased the substrate's surface hardness from 5.8 to 13.5GPa. Simple Ti interlayer could improve a-C:H adhesion to substrate but led to huge area hertzian spallation under scratch load of approximately 98mN. Adding the Ti-a-C:H:Ti gradient interlayer could prevent huge area delamination for critical loads up to 262mN without significantly affecting the top a-C:H mechanical properties. Additionally, the COF between substrate and Berkovich stylus during scratch testing decreased from 1.26 for uncoated sample to 0.03 for a-C:H coated sample. No change in grain structure near substrate surface was examined for deposition temperatures up to 135°C.

Wear of Flame-Sprayed Ni-Cr-B-Si Powder Coating on Journal for Seal Contact

Flame-sprayed techniques is used in this paper to coat Ni-Cr-B-Si powder on low-carbon steel or bearing steel materials of the journal surface. The wear tester is used to explore material properties of the binding capability, surface hardness, wear and friction within each layer depth. The normal force is applied in addition to the cladding layer by not only using bearing ball but also oil seal pieces, to explore rubber material of oil seal contact journal. In experiments to explore the material and processing conditions affect the microstructure and hardness of the cladding layer, and at the same hardness, surface roughness to affect the performance of the mill run.The results showed that spraying Ni-Cr-B-Si alloy powder in mild steel sheet to melt and run, cladding layer and the substrate has a uniform distribution of fine abrasive particles and binding effect, causing the substrate surface hardness (HRC) about promotion 10 times. While, if sprayed Ni-Cr-B-Si alloy powder to steel panels bearing surface because the surface coated compact structure, can reduce the surface roughness and the coefficient of friction, and more improve the wear resistance of the cladding layer.

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

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.

Microstructure and wear resistance of molybdenum based amorphous nanocrystalline alloy coating fabricated by atmospheric plasma spraying

Molybdenum (Mo) based amorphous nanocrystalline coating was deposited on the surface of plain carbon steel substrates by atmospheric plasma spraying (APS). X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the microstructures of Mo-based powder and coating. The surface hardness of substrate and coating were determined using a Vickers hardness tester, and microhardness profile of cross-section was realized by a Vickers microhardness tester. Wear tests were carried out using a pin on plate type tester by changing the load and linear speed. The results indicated that the as-prepared Mo-based coating was mainly composed of Fe0.54Mo0.73, Fe3Mo, Cr9Mo21Ni20, Fe3B and Cr0.46Mo.4Si0.14 phases. The average grain size of Mo-based coating was 22–32nm. The coating presented a dense layered structure and its thickness was about 250μm. The surface hardness of Mo-based coating was as high as 9.2GPa, which was 8 times of substrate. The microhardness along the cross-section gradually decreased from coating to substrate. The wear resistance of Mo-based coating was far better than that of substrate.

Improvement of Tribological Properties of Mosa Films by Forming Interlayers and/ or Bombarding with Ions

ABSTRACTThe effects of forming interlayers and/or bombarding with ions on the tribological properties of the sputter-deposited MoS2 films were investigated. The MoS2 films on substrates of Ti-alloy, martensitic stainless steel and high speed tool steel with TIN interlayers were evaluated by ball/disk sliding tests under ultra-high vacuum condition. Furthermore, nitrogen- or sulfer-ion-bombarded MoS2 films tested too. The test results showed correlation between the surface hardness of substrates and the wear life of MoS2 films. The wear life of the ion-bombarded MoS2 films was improved by mixing film/substrate interface.