Brazed Diamond Research Articles

Research on laser brazing diamond coating process based on temperature field finite element simulation and machine learning

The temperature of laser brazing diamond seriously affects the quality and service life of diamond tools. In this study, a finite element model of laser brazing diamond was established to achieve digital control of the temperature field during the brazing process. It was determined that the main energy of diamond warming comes from the heat conduction of the molten pool. The maximum temperature value within the brazing layer was proposed as an important indicator of the quality of diamond coating formation. The correlation and local sensitivity of each process parameter to the maximum value of temperature were calculated by a neural network-based machine learning method, and the influence of process parameters on the temperature field was explored. The result of the theoretical analys was finally verified by the coating wear-resistance experiments, and the wear-resistance of the diamond coatings was significantly better than that of other cases when the maximum temperature value in the brazing process was in the range of 1100 °C–1130 °C.

Research status of crack problem in laser brazing diamond

Research status of crack problem in laser brazing diamond

Crack characteristics of pulsed laser brazed diamond grinding wheel

Experiments on pulsed laser brazing of diamond grinding wheels were carried out in this paper. The crack characteristics and residual stress of brazed layer were detected and evaluated. The influence laws of pulse width, frequency, diamond mixing ratio, number of stacked layers, powder thickness and preheating temperature on crack characteristics were investigated. The pulsed laser characteristic coefficients (peak pulse power density/pulse interval time) and the correlation law between thermal stresses and cracks are discussed. The results show that the pulse width and frequency of the pulsed laser affect the cracking rate by varying the energy input and the time between pulses. The existence of a suitable value for the pulse characteristic coefficient corresponding to pulse width and frequency corresponds to a lower cracking rate. Thermal stress variations due to changes in process conditions at different diamond percentages, number of stacked layers, and preheating temperatures are the main causes of crack rate variations. Cracking is not only affected by thermal stresses, but also by the quality of the formed surface when pulsed laser brazing diamond to nickel–chromium alloy brazing material. For example, the main reason for the variation in cracking rate is the change in the morphology of the molded surface due to the variation in the thickness of the powder spread at different variations in the thickness of the powder spread.

Comparative study on induction brazing of diamond with rare earth Nd-doped crystalline and amorphous Ni-based filler alloy

This essay aims to comparatively study the microscopic morphology and grinding properties of brazed diamonds with amorphous and crystalline filler alloy in the case of rare-earth Nd-doped modified Ni-based filler alloy. The results show that at the same content of Nd, Cr7C3 is mainly generated at the brazing interface of crystalline samples. In contrast, Cr27C6 is mainly generated at the brazing interface of amorphous samples. Amorphous solder material achieves a robust chemical metallurgical union, producing a dense and homogeneous carbide layer. The bonding strength between amorphous solder material and diamond is further enhanced. The addition of rare earth element Nd contributes greatly to the forming ability of amorphous filler alloy. Nd atoms in the amorphous solder material readily bond with Ni atoms, reducing the chemical corrosion of Ni atoms on diamonds and resulting in a lower degree of graphitization. When the amount of Nd added is 1.0 wt%, the morphology of amorphous filler alloy brazing diamond is more complete than the effect of the crystalline state, the degree of thermal damage is lower, and the surface of amorphous filler alloy brazing is smoother. Frictional wear experiments show that the amorphous filler alloy holds diamond better than the crystalline filler alloy, and the diamond specimens prepared with the amorphous filler alloy demonstrate a significantly superior grinding performance in comparison to the diamond specimens prepared with the crystalline filler alloy.

Optimization of brazing process and structure lightweight design for diamond microchannel

The application of diamond material significantly improves the heat dissipation capability of liquid cooling microchannels, solving the bottleneck problem of heat dissipation for highly integrated electronic components and thus promoting the development of a new generation of military electronic equipment. In this study, diamond microchannels with ultra-high heat flux density were reliably vacuum-brazed by using AgCuTi filler metal in a high vacuum furnace. Microstructure and properties of diamond brazing joints were studied and effect of brazing temperature and time was analyzed. The optimal brazing process parameters were obtained as follows: a vacuum level of <1×10−5 Pa, brazing temperature of 840°C, brazing pressure of 0.5–3 bars and holding time of 10 min. Following vacuum-brazing experiment, the brazing residual stress and working stress of the diamond microchannel were analyzed by finite element simulation. The wall thickness of the diamond microchannel was optimized. The minimum wall thickness, which was 0.4 mm, was obtained for the diamond microchannel with dimensions of 14 mm × 10 mm × 1.3 mm. On that basis, the influence of brazing pressure on the brazing filler overflow in the diamond microchannel brazing process was studied. It was showed that when the pressure was below 1 bar, the overflow of brazing filler from the brazing seam could be controlled to a minimum, especially suitable for brazing precision. The formation of residues in the diamond microchannel was thereby avoided basically, and a diamond microchannel heat sink with good performance was obtained.

Effects of Ge on microstructure evolution of the Cu-based filler metal and the Cu-20Sn-10Ti-1Ga/diamond brazing mechanism

Effects of Ge on microstructure evolution of the Cu-based filler metal and the Cu-20Sn-10Ti-1Ga/diamond brazing mechanism

First-principles Calculations and Experimental Study on Interface Strengthening of Brazed Diamond with Ni-Cr Filler

First-principles Calculations and Experimental Study on Interface Strengthening of Brazed Diamond with Ni-Cr Filler

Wear characteristics of brazing diamond abrasive wheel on high efficiency grinding ferrous metals

A kind of diamond abrasive grinding wheel was brazed in high vacuum furnace using Ni–Cr–P–Si active powder filler alloys. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Raman spectra and X-ray diffraction (XRD) technique analysis were applied to investigate the wear characteristics of brazing abrasive grinding wheel during the process of dry cutting ferrous metal and the interface characteristics of brazing diamond grains to steel substrate. The reaction products such as Cr7C3 and Cr3C2 carbides with columnar shape were formed toward around the diamond brazed interface. The results showed that diamond brazing abrasive wheel had an advantage in terms of more high efficiency and safety than resin grinding wheel during the process on cutting ferrous metals. The main tool wear model was abrasive grains broken, fracture and corrosion which were near the brazed interface. It revealed that the cutting chips were adhered to the surface of broken grains and covered the abrasive grits during the cutting process where arising high temperature on the grinding arc zone. Results proved that the graphitization phenomenon of diamond grits was slightly occurred and the diamond bonding strength was strong enough to meet the requirements of high efficiency and heavy load machining on dry cutting cast iron. The experiment also demonstrated that a kind of safety, high strength and super sharp diamond abrasive wheel could raise machining efficiency on cutting ferrous metal materials.

Active laser brazing of diamond onto 45 steel: Diamond flow behavior, microstructure and bonding strength

The paper investigated the influence of an active agent on the distribution and bonding properties of laser brazed abrasive particles experimentally in fabricating a diamond tool. In the design of experiments, fiber laser brazing was applied to make a single-layer diamond tool, 45 steel was used as a substrate, Cr2O3 was used as an active agent, and Ni-Cr alloy was used as a filler metal. The advantages of active laser brazing(A-LB) and conventional laser brazing (LB) are compared and analyzed from the aspects of flow behavior and mechanical properties. The experimental findings demonstrate that the molten metal flowing to the central will cause the diamond particles in A-LB to flow to the central of the molten pool. The diamond and Ni-Cr interface on the A-LB specimen is roughly 10 μm broader than on the LB. A-LB has a higher single particle shear strength than LB. Additionally, the sample of A-LB has superior wear resistance.

Wear resistance of laser brazing diamond coating with and without pre-machining V-groove on diamond surface

The wear resistance of laser brazing diamond coating with and without pre-machining V-groove on the diamond surface was investigated. The size of V-groove at the surface of diamond machined by laser was about 60°, and the edge length was around 120°. The wear loss of V-groove diamond brazing coating was smaller than that of noncut diamond brazing coating under the same laser power and friction load conditions. Thus, the wear resistance was significantly improved by pre-machining V-grooves on the diamond surface using laser. The V-groove is functioned as a ‘rivet’ diamond particles, greatly enhancing the diamond’s anti-spalling performance throughout the wear process. Moreover, the wear loss of diamond brazing coating fabricated by laser power of 1.1 kW was smaller than that of 1 kW laser power. The wear loss of laser brazing coating is increased as the load is increased.

Interfacial microstructures and Grinding performance of Synthetic Diamond Grits brazed by Cu-22Sn-3Cr Alloy

To ensure the reliable bonding and low thermal damage of brazed diamond grits, a Ni-free Cu-Sn-Cr filler alloy was developed based on our previous study. Interfacial microstructure of diamond grits brazing used by Cu-22Sn-3Cr (in wt. %) filler alloy at 950 °C for 5, 10, 20, and 40 min were systematically investigated. Only Cr7C3 was generated at the interface between diamond and Cu-22Sn-3Cr alloy, and the thickness of Cr7C3 was increased after extended brazing time. The grinding performance of diamond tools brazed using Cu-22Sn-3Cr alloy has fewer ratios of diamond grits with breakage and fall-off failures and thus was found to be superior to that brazed by Ni-14Cr-10P filler alloy. In addition, alloy composition has a more significant influence than brazing time on the interfacial microstructure and mechanical behavior of brazed diamond grits; and the higher mechanical behavior of diamond grits brazed using Cu-Sn-Cr filler alloy is proved to be closely related to the low solubility of C in Cu-Sn-based alloy. Results obtained in this work are also crucial for developing a diamond brazing technique to fabricate diamond-related materials and devices.

Interfacial characteristics and thermal damage of brazed W-coated diamond with Ni- based filler alloy

In this study, the brazing of W-coated diamond to 1045 steel with Ni-based filler alloy was investigated. In addition, the brazing thermal damage of W-coated diamond joints was compared to that of uncoated ones. After brazing, the coating was not fount to affect the good wettability of the Ni-based filler alloy to the diamond. Moreover, the cracks at the interface of W-coated diamond were less and smaller. An ordered and compact Cr3C2 layer was formed on the surface of the uncoated diamond, while a disordered Cr3C2 layer and rod-like Cr7C3 growing into the filler alloy were formed on the surface of the W-coated diamond. The chromium carbide layer on the W-coated diamond surface was thinner, the graphitization degree was lower, and the maximum residual compressive stress was reduced by 11.4% compared to those on the uncoated diamond. The mechanical properties of the W-coated diamond grits were better preserved after brazing, and the coating alleviated the thermal damage of the brazed diamond joint.

Fabrication and performance of brazing diamond using large size Ni[sbnd]Cr alloy as a bonding agent

To obtain the brazing effect of good exposure of abrasive particles and uniform thickness of the solder layer, the concept of vacuum brazing diamond with large particle size alloy solder was proposed, and the geometric model was established. The equation group of the relationship between large particle size alloy solder and diamond particle size was obtained, and the practical solution based on the wetting angle of alloy solder was obtained. In this study, NiCr alloy particles were used as the bonding agent and four sets of controlled experiments with different size combinations were conducted. The intermediate interface was analyzed by scanning electron microscopy and X-ray energy spectrometer. According to the test results, it demonstrated a large size NiCr alloy provides high consistency after brazing. Carbide chromium compound was also founded at the interface between diamond and alloy, which realized the firm control of diamond. This study showed that the new diamond brazing process based on the particle size matching mechanism was a feasible and promising method.

Property Research on Diamond Tool Machining Sapphire Dome

Brazing diamond tools were used to machining monocrystal sapphire dome. The effects of processing parameters on the cutting force, surface quality were researched. The results showed that the speed of bowl-type tool greatly affects the mechanical properties. The autorotation speed of workpiece effect less. The surface roughness of sapphire dome average at about 1.7 µm after machining. A large number of gully left on the sapphire dome surface. The processing chips were in the debris shapes.

Promoting the bonding strength and abrasion resistance of brazed diamond using Cu–Sn–Ti composite alloys reinforced with tungsten carbide

Abstract Diamond brazing is widely used in manufacturing wear–resistant tools. However, designing Cu–based filler metals with good welding characteristics and excellent mechanical properties remains a challenging task. In this work, diamond particles were connected to Q460 steel by using Cu–Sn–Ti composite fillers reinforced with different contents of micron–scale tungsten carbide (WC) particles. The microstructure of the brazing interface was analyzed via scanning electron microscopy and energy dispersive spectroscopy. The phase constitution of the brazed seam was characterized via X–ray diffraction. The effects of adding reinforcement on the mechanical properties of the vacuum brazed diamond samples were comprehensively analyzed and discussed. Results showed that the connection between diamond particles was effectively promoted by the addition of 15 wt% WC particles to the Cu–Sn–Ti fillers. The diamond and steel matrix were closely connected because of the formation of TiC and Cu Ti compounds. Samples with 15 wt% WC had a higher shearing strength and a lower abrasion loss than samples with different WC contents. Morphological examination of the wear surface showed that the interface reaction between WC and Cu–based filler alloys was tightly connected. Reinforcement with WC effectively improved the bonding strength and wear resistance of the samples. • The WC reinforced particles were added into Cu-Sn-Ti filler alloys to promote the strength and hardness. • The excessive wetting reaction was inhibited, and the exposure height of diamond particles was increased. • The effective grinding area was increased with the WC particles adding into fillers. • The shearing strength of the samples was significantly increased due to the WC reinforced Cu-Sn-Ti filler metals. • The coefficient of friction and grinding obstacle were lower, and the grinding performance was significantly improved.

Influence of laser scanning speed on the formation property of laser brazing diamond coating

The pre-placed BNi-2 alloy solder was utilized as braze material to fabricate brazing diamond coating on 65Mn steel substrate by using fiber laser with 5 mm × 5 mm square laser spot. The laser spot was scanned at a steady power of 1.1 kW. The effect of laser scanning speed on the formation mechanism was investigated. Different scanning speed leads to different heating conditions of solder layer, and finally leads to different melting behavior of the coating. At the small laser scanning speed (1 mm/s and 2 mm/s), the solder can be fully melted to form a small liquid ball owing to the long interaction time, and the small ball can quickly flow into the left liquid molten pool because of the high heating temperature and good fluidity. Because of its small mass, the diamond particles float on the surface of the molten pool and gather on the top of the molten pool. With the cooling and solidification of the molten pool, the diamond particles are finally fixed on the top of the coating. With the increase of laser scanning speed (3 mm/s), the solder which has not been completely melted will flip the coating toward the liquid molten ball due to the greater melting imbalance in the solder area. The initial liquid molten balls constantly gather and grow in size and finally contact with the molten pool and merge into it. However, when the scanning speed reaches 4 mm/s, the solder cannot be fully melted due to the shortening of the irradiation time of the laser spot. The graphitization degree of diamond, the exposed height of diamond and the width of coating were also studied and they are related to the previous formation process.

Brazing diamond grits onto AA7075 aluminium alloy substrate with Ag–Cu–Ti filler alloy by laser heating

The brazing of diamond is a promising way to fabricate grinding wheels for efficient machining and precision grinding. This work investigated the feasibility of bonding diamond grits onto Aluminium Alloy 7075 (AA7075) substrate with a Ag–Cu–Ti filler alloy via laser fusion brazing. The interfacial microstructures and the strength of the brazed diamond joints were studied. The cross-section of the brazed diamond joint consists of a molten filler alloy layer, a molten pool, a heat effect zone, a columnar crystal zone and an equiaxed crystal zone. Within the interface of the filler alloy/substrate metal, microstructures observed possibly were Ag(s.s), Al(s.s), TixAl, Al2Cu and Mg intermetallic compounds. A layer of TiC with a thickness of about 30–50 nm was found at the bonding interface of the diamond/filler alloy. The averaged peak shear force of the brazed joints was found to be approximately 39.8 N. The abrasion grinding test indicated that the diamond/AA7075 brazed joint was adequate for grinding. However, the pulled-off of grit was found to be the primary failure of this type of brazed joint. This work broadened the brazing diamond technique and the range of applications of brazed diamond wheels for efficient grinding.

Grinding of alumina ceramic with microtextured brazed diamond end grinding wheels

Brazed monolayer diamond grinding wheels have advantages of a high abrasive bonding strength, high protrusion, and a large chip disposal space. However, it is difficult to prepare ordered and fine-grained brazed diamond grinding wheels. This study presents a new method for grain-arranged, brazed diamond grinding wheels with microtextures with similar performance to ordered and fine-grained brazed diamond grinding wheels. First, coarse diamond grains (18/20 mesh) were orderly brazed to fabricate the end grinding wheels. Next, a series of microtextures were ablated on the diamond grains using a pulsed laser, and two types of textured end grinding wheels—TG-G (ablated microgrooves only) and TG-GH (ablated microgrooves and microholes)—were prepared. Then, an experiment involving the grinding of alumina ceramics was performed, and the grinding characteristics and grinding mechanism were analyzed. The results indicated that compared with untextured diamond end grinding wheels (TG), the textured diamond grinding wheels (TG-G and TG-GH) significantly reduced the grinding force and the roughness of the machined surface. The local stress concentration at the microtextures promoted the formation of microcracks in the diamond grains of TG-G and TG-GH, and the self-sharpness of the grinding wheel was significantly improved. The brittle fracture mode of ceramic materials in grinding included intergranular fracture and transgranular fracture. Ironing pressure action was a key material-removal mechanism. It had an important influence on the cutting force and plasticity characteristics of the TG machined surface. For the surfaces processed by TG-G and TG-GH, the effect of ironing was weakened, while shearing played a more important role. The TG-GH grinding wheel ablated with microgrooves and microholes was superior to the TG-G grinding wheel ablated with only microgrooves, with regard to the grinding force, roughness, and self-sharpening.

Laser power effects on properties of laser brazing diamond coating

ABSTRACT Effect of laser power on formation mechanism of laser brazing diamond coating has been investigated for the first time and its interface microstructure was also investigated. The BNi-2 alloy solder was utilized as braze material to fabricate brazing diamond coating on 65Mn steel substrate by using fiber laser. The laser spot was scanned at a steady speed 3 mm/s. With increase in laser power, BNi-2 alloy solder layer gradually melts and spreads fully until a laser power of 1.1 kW was reached. A further increase in laser power results in intense graphitization of the surface of the diamond grits and thermal damage. The breakage of diamond is observed when laser power is increased to 1.3 kW. Four steps are observed in laser brazing process: melting, gathering, fusing and spreading. The microstructure investigation indicates that both Cr3C2 and B4C carbides are formed at the interface between diamond and BNi-2 alloy matrix.

Performance and wear of brazing diamond grinding disc in machining gray cast iron

To improve the machining efficiency of cast iron and the service life of cutting tools, a brazing diamond grinding disc was designed and fabricated. Experiments regarding the production efficiency, service life, and cutting temperature were conducted to compare the brazing diamond grinding disc and the traditional resin sand wheel sheet grinding gray cast iron HT150. The results demonstrated that the grinding efficiency and service life of the brazing diamond grinding disc were higher than that of the resin sand wheel sheet, the grinding temperature was lower than that of the resin wheel sheet, and the wear behavior of the diamond abrasive grains was mechanical wear with no chemical wear. This shows that machining gray cast iron with the brazing diamond grinding disc is feasible.