A Ni-Cr-B-Si coating technique was developed and successfully applied on austenite grey iron substrate in a conventional resistance furnace under graphite powder protection. The microstructure, phase distribution, che...A Ni-Cr-B-Si coating technique was developed and successfully applied on austenite grey iron substrate in a conventional resistance furnace under graphite powder protection. The microstructure, phase distribution, chemical composition profile and microhardness along the coating layer depth were investigated. Shear strength of the coating was also tested. Microanalysis shows that the coating is consist of γ-Ni solution and γ-Ni+Ni3B lamellar eutectic, as well as small amount of Cr5B3 particles. Diffusion induced metallurgical bonding occurs at the coating/substrate interfaces, and the higher the temperature, the more sufficient elements diffused, the broader interfusion region and the larger bonding strength, but it has an optimum value. And the bonding strength at the interface can be enable to reach 250-270 MPa, which is nearly the same as that of processed by flame spray. The microhardness along the coating layer depth shows a gradient distribution manner.展开更多
The wear behavior of Ni-Cr-based alloys was investigated at ambient and elevated temperatures. The wear samples were prepared by metallurgical hot pressing. Wear tests were carried out on a general purpose wear testin...The wear behavior of Ni-Cr-based alloys was investigated at ambient and elevated temperatures. The wear samples were prepared by metallurgical hot pressing. Wear tests were carried out on a general purpose wear testing machine having a heating unit and pin-disc sample configuration. The counterface material was prepared from Al2O3 ceramics. The tests were carried out at room temperature(RT),200 ℃ and 600 ℃. The effects of temperatures on the tribological properties were determined by using optical microscopy,and X-ray diffractometry. The results show that at room temperature the worn surfaces of the alloys are characterized by mild scuffing and micro cracks,the action of nano-crystal structural wear debris on the worn surfaces is responsible for the reduction of friction. At 200 ℃,the friction coefficient is the highest. The worn surfaces of the alloys are adhesive and oxidative. At 600 ℃,the friction coefficient is reduced due to the effect of the oxides,tungstates and sulfides residue on the worn surface.展开更多
利用高能球磨和真空热压烧结技术制备了Ni Cr Mo和Ni Cr Mo Al两种不同的合金.研究了Al元素对合金的微观组织结构和机械性能的影响,考察了不同温度(RT^900℃)条件下合金的摩擦磨损性能,并对磨损机理进行分析.结果表明:Al元素的加入减少...利用高能球磨和真空热压烧结技术制备了Ni Cr Mo和Ni Cr Mo Al两种不同的合金.研究了Al元素对合金的微观组织结构和机械性能的影响,考察了不同温度(RT^900℃)条件下合金的摩擦磨损性能,并对磨损机理进行分析.结果表明:Al元素的加入减少了合金粉末的团聚,促进了烧结过程中合金晶粒的长大,提高了合金的致密度和硬度;尤其在高温摩擦环境中,与Ni Cr Mo合金相比,含有Al元素的Ni Cr Mo Al合金能在摩擦表面形成由Mo O3、Ni O和Ni Mo O4等组成的摩擦层,且没有Cr2O3硬质相的生成,极大提高了其高温下的摩擦学性能.展开更多
基金The paper is supported by country-level Spark Plan in 2003,project No.: 2003EA690034.
文摘A Ni-Cr-B-Si coating technique was developed and successfully applied on austenite grey iron substrate in a conventional resistance furnace under graphite powder protection. The microstructure, phase distribution, chemical composition profile and microhardness along the coating layer depth were investigated. Shear strength of the coating was also tested. Microanalysis shows that the coating is consist of γ-Ni solution and γ-Ni+Ni3B lamellar eutectic, as well as small amount of Cr5B3 particles. Diffusion induced metallurgical bonding occurs at the coating/substrate interfaces, and the higher the temperature, the more sufficient elements diffused, the broader interfusion region and the larger bonding strength, but it has an optimum value. And the bonding strength at the interface can be enable to reach 250-270 MPa, which is nearly the same as that of processed by flame spray. The microhardness along the coating layer depth shows a gradient distribution manner.
基金Project(K1703060819) supported by the National Defence Basic Research of China
文摘The wear behavior of Ni-Cr-based alloys was investigated at ambient and elevated temperatures. The wear samples were prepared by metallurgical hot pressing. Wear tests were carried out on a general purpose wear testing machine having a heating unit and pin-disc sample configuration. The counterface material was prepared from Al2O3 ceramics. The tests were carried out at room temperature(RT),200 ℃ and 600 ℃. The effects of temperatures on the tribological properties were determined by using optical microscopy,and X-ray diffractometry. The results show that at room temperature the worn surfaces of the alloys are characterized by mild scuffing and micro cracks,the action of nano-crystal structural wear debris on the worn surfaces is responsible for the reduction of friction. At 200 ℃,the friction coefficient is the highest. The worn surfaces of the alloys are adhesive and oxidative. At 600 ℃,the friction coefficient is reduced due to the effect of the oxides,tungstates and sulfides residue on the worn surface.
文摘利用高能球磨和真空热压烧结技术制备了Ni Cr Mo和Ni Cr Mo Al两种不同的合金.研究了Al元素对合金的微观组织结构和机械性能的影响,考察了不同温度(RT^900℃)条件下合金的摩擦磨损性能,并对磨损机理进行分析.结果表明:Al元素的加入减少了合金粉末的团聚,促进了烧结过程中合金晶粒的长大,提高了合金的致密度和硬度;尤其在高温摩擦环境中,与Ni Cr Mo合金相比,含有Al元素的Ni Cr Mo Al合金能在摩擦表面形成由Mo O3、Ni O和Ni Mo O4等组成的摩擦层,且没有Cr2O3硬质相的生成,极大提高了其高温下的摩擦学性能.
