PSI - Issue 20

Sharin P.P. et al. / Procedia Structural Integrity 20 (2019) 236–241

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Sharin P.P. et al. / Structural Integrity Procedia 00 (2019) 000–000

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Novikov et al. (2004) and Konovalov et al. (2009). According to Hsieh and Lin (2001), Isonkin et al. (2013), Naidich and Kolesnichenko (1967), Semenov et al. (1974), Tillmann et al. (2013, 2015) the most appropriate metal matrices from the point of increasing diamond retention in composites contain carbon-reactive metals of the transition group. Thus, the actual direction of research on the diamond-containing composites with high diamond retention development is to identify formation patterns of the diamond-matrix interphase zone structure during high temperature contact interaction of diamond with carbide-forming metals in vacuum. Despite a significant amount of fundamental work by Artini et al. (2012), Hsieh and Lin (2001), Huang et al. (2007), Kushatlova et al. (1984), Loktyushin et al. (2009), Margaritis (2003), Nozhkina (1988), Qiu et al. (2012), Sharin et al. (2016), Stasyuk et al. (1984), Tillmann et al. (2013, 2015), Uemura (2004), Wang et al. (2002), and Yakhutlov et al. (2011) devoted to the contact interaction of diamond with carbide-forming metals at high temperatures, reaching up to melting temperatures, some issues and aspects of the diamond-metal transition zone structure formation, which are necessary to select diamond-containing composites compositions and manufacturing technologies, remain open and require clarification and additions. The purpose of the work is to study microstructure and phase composition of the diamond-metal transition zone, formed as a result of contact solid-phase interaction of diamond with chemically active carbide-forming metals - chromium, cobalt, iron and titanium in vacuum - at temperature heating conditions, which are used in sintering cemented carbide matrices of diamond tools with self-dosed copper impregnation.

Nomenclature F

breakout force contact area, m 2

S

SEM

Scanning electron microscopy

P

load, applied during sintering of contact pairs

σ cont

diamond-metal contact strength

2. Experimental procedure To obtain diamond-metal contact pairs, natural diamond crystals and metal powders, pressed in the form of tablets with 6 mm in diameter under pressure of 45–75 MPa, were used. Characteristics of the used metal powders are listed in Table 1.

Table 1. Metal powder characteristics. Metal powder

Grain size ( μ m )

Chromium

100-120 40-100 40-100 40-100

Cobalt

Iron

Titanium

Natural diamond crystals were round brilliants with seventeen facets, faceted and polished in the factory. The mass of diamonds was ~0.01 carats their girdle diameter was ~1.60±0.015 mm. The crystals were transparent and had a slightly yellowish tint. Each diamond was placed on the flat surface of the metal tablet in such a way that its polished area was tightly attached to the tablet surface (Fig.1a). A load P=17.5 grams was applied to each sample from the diamond side through a graphite rod. In this position, the samples were placed in a vacuum furnace chamber and subjected to heating The heating mode corresponded to the vacuum furnace operation mode during sintering of diamond containing matrices of tools based on hard alloy powder mixtures impregnated with copper (Fig.1b). After completion of the heating cycle, the furnace was turned off and the temperature in the furnace chamber with the samples decreased in the free cooling mode.