Powder metallurgy T15 tool steel: Part II. Microstructure and properties after heat treatment

The effect of powder particle size and heat treatment on the micro structure and properties of hot isostatically pressed (“hipped”) T15 tool steel has been evaluated. Gas-atomized powder was screened into size fractions covering the range of ≤44 to 1200 /i-m and hipped at 1130 ‡C or 1195 ‡C. The consolidated powders were austenitized at 1175 ‡C or 1225 ‡C and tempered at 538 ‡C, 552 ‡C, or 565 ‡C to control prior austenite grain size, carbide type, carbide volume fraction, and carbide size distribution. Properties measured were bend strength, C-notch impact toughness, and hot hardness. Prior austenite grain size increases with hot isostatic pressing (“hipping”) temperature and austenitizing temperature but is independent of the particle size; similarly, the influence of austenitizing temperature on dissolution of MC and M₆C is independent of the particle size. In each particle size fraction, the volume fraction and size distribution of MC are independent of the tempering temperature. For M₆C, the volume fraction increases and the size distribution is skewed to coarser sizes with increasing tempering temperature. No significant differences in strength and toughness were detected as a function of particle size. Hot hardness is not affected by the particle size. The hot hardness of a powder blend (≤1200 Μm) hipped at 1130 ‡C was superior to that of commercial powder metallurgy (PM) T15 tool steel hipped at 1195 ‡C; this is attributed to a finer carbide size in the noncommercial material. It is established that the subcommercial hipping temperature (1130 ‡C) results in significant microstructural refinement; there is an associated small amount of residual porosity, and this controls the mechanical properties.     

热处理工艺对ZTC4钛合金显微组织及性能的影响研究

采用金相显微镜(OM)研究了热处理制度对ZTC4钛合金显微组织的演变规律,以及显微组织对力学性能的影响关系.结果表明:ZTC4钛合金铸件由马氏体α'相组成,进行退火以及热等静压+退火热处理后,显微组织均为典型魏氏组织.ZTC4钛合金铸件退火后抗拉强度可达955 MPa,其延伸率和断面收缩率分别为8.8％和13.1％.采...     

TiAl合金建筑材料焊后热处理组织及性能研究

对建筑用TiAl合金电子束焊接接头进行了两种热处理试验研究,借助金相显微镜(OM)分析了接头不同区域的显微组织,并对焊接接头进行显微硬度测试,分析了两种热处理方式对建筑TiAl合金焊接接头组织及硬度带来的变化.研究表明,TiAl合金电子束焊接后焊缝组织主要为α2相,B相与O相.焊接接头局部热处理后接头硬度较高的区域有所...     

Research on the heat treatment of tool steel 5Cr15MoV

Tempered tool steel 5Cr15MoV was normalized at different temperatures followed by air-cooling.It is found that the hardness increases with the increment of a normalizing temperature from 950℃ to 1 150℃,and it then decreases with the temperature getting higher.The Thermo-calc calculation reveales that the mole fraction of carbides decreases when the normalizing temperature increases,which indicates that more carbon dissolved in the matrix enhances the hardness of the steel.However,the existence of retained austenite causes hardness reduction when the normalizing temperature is over 1 150℃.The salt spray test shows that the steel possesses poor corrosion resistance when it is normalized at a temperature above 1 100℃.The precipitation of the carbides in the cooling process creates a number of chromium-depleted zones,making the steel vulnerable to corrosives.In the present work,an appropriate normalizing temperature is suggested.     

Structure formation in the heat treatment of alloy steel bar

The structure formation in 42Cr4Mo2 electrosteel on continuous cooling is studied. The results are presented in the form of a thermokinetic diagram. It follows from the diagram that bainite structure is predominantly formed in thermochemical treatment with cooling of the rolled steel at a mean-mass rate of 0.4–1.0°C/s, while ferrite-pearlite structure is mainly formed at rates less than 0.4°C/s. The influence of the treatment temperature and time on the structure and properties of the chromomolybdenum steel is investigated. If the cooling rate after hot deformation is increased by a factor of 1.6, the proportion of bainite in the metal is greater. In subsequent annealing with isothermal holding at 650–680°C, the bainite accelerates the spheroidization of the carbides. Consequently, the holding time may be reduced from 6.5 to 4 h, with consequent energy savings but without loss of metal quality.     

Developing regimes for the heat treatment of tool steel 1.2344 with a specific structure

A regime for heat-treating forgings of steel 1.2344 (the analog of steel 4Kh5MF1S) has been developed, tested, and optimized to ensure that the structure of the forgings meets the requirements of the NADCA standard and specification SEP 1614. A study was made of the microstructure of forgings of steel 1.2344 after annealing and normalizing under different conditions. It was found that the structure of the forgings made in the forging-extrusion shop at Spetsstal’ meets the NADCA standard and specification SEP 1614 when the forgings are subjected to normalizing and tempering.     

热处理工艺对Cu-Ni-Si合金组织与性能的影响

采用3种不同的工艺(直接在450℃下进行时效处理;80%冷轧,然后在450℃下进行时效处理;600℃/8 h高温预时效+80%冷轧+780℃/2 min+450℃/16 h终时效)对固溶处理后的Cu-2.0Ni-0.34Si-Mg合金进行形变热处理,研究形变热处理工艺对该合金的组织与硬度及电导率的影响。结果表明:采用第3种工艺对合金进行形变热处理,由于其中的短时高温预处理可以获得溶质原子充分固溶的过饱和固溶体,因此终时效后的合金具有最佳的综合性能,显微硬度为180 HV,相对电导率为49.8%IACS,伸长率为13%。合金的平均晶粒尺寸约为20μm,主要析出强化相为δ-Ni2Si。     

基于电子束增材制造的TC4钛合金成形件热处理性能研究

将电子束选区熔化制备的试件增加热处理工艺,利用扫描电子显微镜和金相显微镜研究了热处理后TC4钛合金试件的组织特征;并通过试件力学性能的变化,揭示了不同热处理工艺选择对电子束选区熔化成形产品的影响.结果 表明:不论是空冷处理还是炉冷处理,试件在相变点温度以下加热其抗拉强度提升,在相变点温度以上加热其抗拉强度会下降.通过观...     

The influence of heat treatment on the structure and properties of a near-α titanium alloy

The microstructure and tensile properties of a near-α titanium alloy, IMI-829 (Ti-6.1 wt pct Al-3.2 wt pct Zr-3.3 wt pct Sn-0.5 wt pct Mo-1 wt pct Nb-0.32 wt pct Si) have been studied after solutionizing (and no subsequent aging) at two different temperatures separately, one above the β transus (1050 °C) and another below the β transus (975 °C) followed by various cooling rates (furnace, air, oil, or water). While 1050 °C treatment resulted in coarse Widmanstätten structures on furnace or air cooling, fine Widmanstätten structure on oil quenching and martensitic structure on water quenching, 975 °C treatment produced duplex microstructures consisting of equiaxed alpha and partially transformed beta phases. Transmission electron microscopy studies revealed the morphology, size, and distribution of the α, β, and martensite phases and also the presence of small ellipsoidal suicide particles and an interface phase with fcc structure at almost all α-β interfaces. The oil quenched structure from 1050 °C has been found to be a mixture of fine Widmanstätten α coexisting with martensite laths and retained beta at the lath boundaries. Silicides with hcp structure of about 0.4 μm size were observed in specimens solution treated at 975 °C. The interface phase is seen in all slowly-cooled specimens. The YS and UTS are superior for 975 °C treatment compared to 1050 °C treatment after water quenching or oil quenching. The tensile ductility values are superior for any cooling rate after 975 °C solution treatment as compared to 1050 °C solution treatment. The specimens failed in tension diagonally by shear after 1050 °C treatment and by cup and cone fracture after 975 °C treatment. In all cases fracture has taken place by microvoid coalescence and in most cases, along the α-β boundaries.     

热处理对FGH95合金组织和性能的影响研究

通过热处理工艺试验设计,研究了不同热处理条件下FGH95合金的组织和性能。与亚固溶线温度热处理后细晶试样比较,过固溶线温度热处理的试样获得了晶粒度8级的相对粗晶组织,强度仅比细晶试样的降低不超过5%,而蠕变性能显著提高,700℃/690MPa条件下,0.2%残余应变的蠕变寿命提高了3～4倍;另外,通过优化γ’相的尺寸与分布,可进一步提高合金的力学性能。     

热处理对GH1016合金组织和性能的影响

为解决GH1016合金在600~800℃温度区间的中温低塑性问题,本文提出一种新的热处理制度.采用1 160℃×30 min炉冷到950℃×120 min,然后空冷的热处理制度,在20~950℃的条件下对处理后的合金试样进行拉伸性能测试并对拉伸断口进行分析.结果表明,经过改进的热处理制度处理后,合金的晶界析出大量的碳化物,阻止了拉伸时裂纹的萌生和扩展,从而提高了合金的塑性.     

Effects of sintering process and heat treatments on microstructures and mechanical properties of VANADIS 4 tool steel added with TiC powders

Abstract

In this study, commercial VANADIS 4 (V-4) tool steel powders were classified by sifting, which was previously the matrix, and fine TiC powder was used as an additive to produce a new material with high hardness and wear resistance, via powder metallurgy and a sintering process. Experimental results showed that the transverse rupture strength of the original V-4 steel powder was 678·5 MPa and was enhanced to 868·6 MPa below 25 μm, after the addition of 35 wt-%TiC powders through sintering at 1400°C. In addition, the hardness increased to 86·2 HRA, transverse rupture strength reached 1059·3 MPa and porosity decreased to 1·2% of the V-4 steel powders (below 25 μm) added with 35 wt-%TiC after sintered at 1400°C and annealed at 850°C, followed by quenching at 1030°C and tempering at 200°C.     

热处理工艺对近α钛合金组织与性能的影响

研究了固溶和时效工艺参数对一种近α钛合金Ti-5Al-2Nb-2Zr-1.5Mo显微组织与力学性能的影响.结果表明:在α+β两相区,随着固溶温度的升高,初生α相含量(体积分数,下同)减少,亚稳相含量增加,冷却过程中分解的针状马氏体α'相使合金的硬度升高;时效温度的变化通过影响α'相分解析出次生α相的尺寸、数量及分布方式...     

热处理工艺对27SiMn钢力学性能的影响

27SiMn液压支架管经过调质热处理来实现其良好的综合力学性能.采用四因素三水平的热处理正交试验,研究了不同热处理工艺参数（淬火温度、淬火保温时间、回火温度和回火保温时间）对力学性能的影响,并确定了最优热处理工艺制度为930℃,40 min淬火和480℃,50 min回火.经最优热处理工艺处理后,其力学性能为：屈服强度895 MPa,抗拉强度1030MPa,伸长率15%,断面收缩率54%,冲击功53.3 J,满足了GB/T 17396—1998标准中对27SiMn钢的性能要求.     

热处理制度对粉末高温合金性能的影响

对比研究了FGH95合金在不同热加工工艺和热处理制度下γ′相的分布，观察了不同热处理制度处理后合金的组织及时效后小γ′相的中心暗场像相，测试了室温（20℃）和高温（650℃）下材料的拉伸性能，并对高温（650℃）瞬时断裂区断口进行了对比分析。结果表明：相同热处理工艺，热等静压温度较高时，时效析出的γ′相尺寸大；不同热处理制度能改变γ′相的分布，盐浴冷却明显增大中等尺寸γ′相数量和合金的高温塑性。     

Effect of heat treatment conditions on the structure and mechanical properties of a cast Al-Li-Cu aluminum alloy

Quenching and one- and two-stage aging conditions are found for a high-strength Al-Li-Cu cast alloy with a low density from the results of studying its structure, mechanical properties, and aging kinetics.     

Infrared brazing of Ti-6Al-4V and 17-4 PH stainless steel with a nickel barrier layer

Infrared brazing of Ti-6Al-4V and 17-4 PH stainless steel using the BAg-8 filler metal was performed in this study. A nickel barrier layer 10 μm thick was introduced on the 17-4 PH stainless steel before infrared brazing. For the specimen that was infrared brazed at 800 °C and 850 °C for less than 300 seconds, the Ni layer served as an effective barrier layer to prevent the formation of Ti-Fe intermetallics. Experimental results show that the average shear strength of the joint can be greatly improved for the specimen by Ni plating. Comparing the specimens with and without electroless-plated Ni film, the former has no Ti-Fe intermetallic compound, but interfacial CuNiTi and NiPTi phases are observed in the latter. The fractured location of the joint after the shear test is changed from the interfacial TiFe (without Ni plating) into the TiCu reaction layer (with Ni plating). The plated Ni layer is consumed for the specimen that was infrared brazed at 880 °C for 300 seconds, and its bonding strength is impaired. Consequently, a lower brazing temperature and/or time are still preferred even though a plated Ni barrier layer is applied.     

热处理工艺对建筑用PC钢棒强韧性的影响

对PC钢棒淬火、回火的热处理工艺、强韧性及其组织和性能的关系进行了系统研究，发现屈强比主要受到淬火温度的影响，当回火温度控制在440－460℃时，能使强度和塑性达到最佳值。尽管在960－1000℃的温度区间淬火屈强比较低，但可以获得较细的显微组织。