Ti(C, N)-TiB2 composite coatings were deposited by means of reactive low pressure plasma spraying (LPPS) based on the technology of self-propagating high-temperature synthesis (SHS). The original powders were mixtures...Ti(C, N)-TiB2 composite coatings were deposited by means of reactive low pressure plasma spraying (LPPS) based on the technology of self-propagating high-temperature synthesis (SHS). The original powders were mixtures of Ti and B4C powders. The powders were mixed by ball mill and then spray-dried and at last sintered to be suitable for spraying. Two spraying distances were selected for LPPS. Scanning electron microscopy (SEM) was used to investigate the morphologies of powders for spraying and the microstructures of the coatings. The phase compositions of coatings were measured by X-ray diffraction (XRD). Spray-dried and sintered powders are denser and better bond than only spray-dried powders. The composite coating is composed of TiB2, TiC0.3N0.7, TiN0.3, Ti4N3-x and impurity phase of Ti5Si3 with 300 mm spraying distance. Partly unreacted B4C powders remained in the coating for 240 mm spraying distance, which may be inadequate reaction. No titanium oxide was detected in the composite coating for the relative high vacuum degree of LPPS. The anti-corrosion property of LPPS sprayed Ti(C, N)-TiB2 composite coating with 300 mm spraying distance in electrolytic solution is superior to that of 240 mm spraying distance. Microhardness of Ti(C, N)-TiB2 composite coating is relatively low due to the unconsolidated structure of the coating. The solving methods to improve property of composite coating are finally put forward in the paper.展开更多
Ti(C,N)-TiB2 cermets were fabricated from Ti(C,N), TiB2, Co and WC powder mixtures via a vacuum hot pressing process. The influence of TiB2 content on their microstructures and mechanical properties was investigated. ...Ti(C,N)-TiB2 cermets were fabricated from Ti(C,N), TiB2, Co and WC powder mixtures via a vacuum hot pressing process. The influence of TiB2 content on their microstructures and mechanical properties was investigated. As a result of the elevated TiB2 contents, two types of corerim microstructures were present in the Ti(C,N)-TiB2 cermets, and remarkably improved mechanical properties were achieved. With the increase of TiB2 content, the flexural strength, fracture toughness and hardness of the Ti(C,N)-TiB2 cermets first increased, and then decreased, while their relative density consistently decreased. Attributed to an integration of the intergranular and intrangranular fracture behaviors, the Ti(C,N)-TiB2 cermets with 20 wt% TiB2 content exhibited the best overall properties with the relative density, hardness, fracture toughness and flexural strength at 99.3%, 1 995 HV, 7.92 MPa·m1/2 and 1 114 MPa, respectively. The underlying mechanism for their enhanced properties was studied in detail.展开更多
Effects of VC/Cr3C2 on the microstructure and mechanical properties of Ti（C,N）-based cermets were studied. The microstructure was investigated by means of optical microscopy, X-ray diffractometry as well as scanning...Effects of VC/Cr3C2 on the microstructure and mechanical properties of Ti（C,N）-based cermets were studied. The microstructure was investigated by means of optical microscopy, X-ray diffractometry as well as scanning electron microscopy in combination with energy dispersive spectrometry. Mechanical properties, such as transverse rupture strength, hardness and fracture toughness, were measured. The results show that there are black core-grey rim structure and white core-grey rim structure in the microstructure. The grains become fine due to the VC/Cr3C2, and the grains of cermet added with 0.75VC/0.25Cr3C2 are refined most remarkably. The black core becomes finer with the increase of VC addition and rim phase becomes thicker with the decrease of Cr3C2 addition. The porosity increases with the increase of VC addition in VC/Cr3C2. Compared with the cermet free of VC/Cr3C2, the transverse rupture strength and hardness of cermets with VC/Cr3C2 are both improved, and the maximum values are both found for the cermet with 0.25VC/0.75Cr3C2. The fracture toughness can be effectively promoted by adding VC/Cr3C2 with an appropriate ratio of VC to Cr3C2, and the maximum value is found for the cermet with 0.5VC/0.5Cr3C2.展开更多
文摘Ti(C, N)-TiB2 composite coatings were deposited by means of reactive low pressure plasma spraying (LPPS) based on the technology of self-propagating high-temperature synthesis (SHS). The original powders were mixtures of Ti and B4C powders. The powders were mixed by ball mill and then spray-dried and at last sintered to be suitable for spraying. Two spraying distances were selected for LPPS. Scanning electron microscopy (SEM) was used to investigate the morphologies of powders for spraying and the microstructures of the coatings. The phase compositions of coatings were measured by X-ray diffraction (XRD). Spray-dried and sintered powders are denser and better bond than only spray-dried powders. The composite coating is composed of TiB2, TiC0.3N0.7, TiN0.3, Ti4N3-x and impurity phase of Ti5Si3 with 300 mm spraying distance. Partly unreacted B4C powders remained in the coating for 240 mm spraying distance, which may be inadequate reaction. No titanium oxide was detected in the composite coating for the relative high vacuum degree of LPPS. The anti-corrosion property of LPPS sprayed Ti(C, N)-TiB2 composite coating with 300 mm spraying distance in electrolytic solution is superior to that of 240 mm spraying distance. Microhardness of Ti(C, N)-TiB2 composite coating is relatively low due to the unconsolidated structure of the coating. The solving methods to improve property of composite coating are finally put forward in the paper.
基金Funded by the National Natural Science Foundation of China(Nos.21571095,51404157)the Zhejiang Provincial Natural Science Foundation of China(No.LY17E050003)+2 种基金the Taizhou Science and Technology Project(No.15gy54)the Open Research Program of Zhejiang Provincial Key Laboratory for Cutting Tools(No.ZD201501)the Open Foundation of Jiangsu Key Laboratory of Precision and Micro-Manufacturing Technology and the Public Projects of Zhejiang Province(Nos.2017C31118,2016C31049)
文摘Ti(C,N)-TiB2 cermets were fabricated from Ti(C,N), TiB2, Co and WC powder mixtures via a vacuum hot pressing process. The influence of TiB2 content on their microstructures and mechanical properties was investigated. As a result of the elevated TiB2 contents, two types of corerim microstructures were present in the Ti(C,N)-TiB2 cermets, and remarkably improved mechanical properties were achieved. With the increase of TiB2 content, the flexural strength, fracture toughness and hardness of the Ti(C,N)-TiB2 cermets first increased, and then decreased, while their relative density consistently decreased. Attributed to an integration of the intergranular and intrangranular fracture behaviors, the Ti(C,N)-TiB2 cermets with 20 wt% TiB2 content exhibited the best overall properties with the relative density, hardness, fracture toughness and flexural strength at 99.3%, 1 995 HV, 7.92 MPa·m1/2 and 1 114 MPa, respectively. The underlying mechanism for their enhanced properties was studied in detail.
基金Project (090414185) supported by the Natural Science Foundation of Anhui Province, China
文摘Effects of VC/Cr3C2 on the microstructure and mechanical properties of Ti（C,N）-based cermets were studied. The microstructure was investigated by means of optical microscopy, X-ray diffractometry as well as scanning electron microscopy in combination with energy dispersive spectrometry. Mechanical properties, such as transverse rupture strength, hardness and fracture toughness, were measured. The results show that there are black core-grey rim structure and white core-grey rim structure in the microstructure. The grains become fine due to the VC/Cr3C2, and the grains of cermet added with 0.75VC/0.25Cr3C2 are refined most remarkably. The black core becomes finer with the increase of VC addition and rim phase becomes thicker with the decrease of Cr3C2 addition. The porosity increases with the increase of VC addition in VC/Cr3C2. Compared with the cermet free of VC/Cr3C2, the transverse rupture strength and hardness of cermets with VC/Cr3C2 are both improved, and the maximum values are both found for the cermet with 0.25VC/0.75Cr3C2. The fracture toughness can be effectively promoted by adding VC/Cr3C2 with an appropriate ratio of VC to Cr3C2, and the maximum value is found for the cermet with 0.5VC/0.5Cr3C2.
文摘研究了Al2O3/Ti(C,N)-Ni-Ti陶瓷复合刀具对淬硬35CrMo合金钢进行连续干切削时各切削参数对切削力的影响.结果表明:切削深度对切削力的影响最显著,切削速度的影响最小.对比研究了Al2O3/Ti(C,N)和Al2O3/Ti(C,N)-Ni-Ti陶瓷刀具的耐磨性能和磨损形态:后者的耐磨性能明显优于前者,其中Al2O3/Ti(C,N)-5%(Ni,Ti)的耐磨性能最高.Al2O3/Ti(C,N)-Ni-Ti刀具的磨损形态主要表现为后刀面的磨粒磨损和疲劳磨损,由于这种材料具有较高的弯曲强度和断裂韧性,能有效防止前刀面出现崩刃破损现象,因此具有较高的可靠性,适用于高速切削.在高速切削条件(ap=0.06 mm,vc=254.9 m/min,vf=0.09 mm/r)下,Al2O3/Ti(C,N)-5%(Ni,Ti)刀具的切削耐用度为150 min.
